Travelling through the former slave states of the American South for a book at around the same time, VS Naipaul became increasingly diverted by the incidence of "very fat people, people who had risen (like dough) to special spheres of obesity - gargantuan, corridor-blocking"; people who "had turned fulfilment and the glory of abundance to personal fat, fat as a personal possession". "It was at times a pleasure and an excitement to see them," Naipaul noted in A Turn in the South (1989), "to see the way each individual human frame organised or arranged its excess poundage: a swag here, a bag there, a slab there, a roll there. A kind of suicide, it might have seemed; but I also began to wonder . . . whether for these descendants of frontier people and pinelanders there wasn't, in their fatness, some simple element of self-assertion."

Although he nowhere suggests it, it is possible that Naipaul - so famously rigorous, so calorie-conscious as a prose stylist, so particular and self-denying (and as slyly satirical as DeLillo) - intended this to stand as a metaphor for the kind of showy, dukes-up, and (as he would see it) disfiguringly steroid-dependent writing, tangy with chemical additives and flavour enhancers, that has been the common currency of American fiction for the last fifty years.

Saul Bellow's third novel, The Adventures of Augie March, the one which showed the fiction writers of America how to stack their plates to overflowing at the five-dollar Eat-All-You-Can buffet of literature, and gave them permission to return for second, even third helpings and fuck Old World notions of politesse and decorum, was published 50 years ago this year. It is an anniversary which has understandably been given the treatment in America, an occasion for retrospection and reminiscence, for magisterial editorials and valedictory, time-of-our-time features. The Library of America has brought out a special commemorative edition of the novel, only the second time a living writer has been so honoured.

"It was the inundation that did it," Vivian Gornick wrote of The Adventures of Augie March in Bookforum magazine. "It came as a literary astonishment, the vividness and the brilliance of it, glowing with the force of its own babble: an onrush, an avalanche, a waterfall of dazzling, inventive complaint pouring out of this manic Jew, this street-smart intellectual, this betrayed lover of art, history, philosophy and women."

"The sentences are like hall closets," Joan Acocella remarked in the New Yorker, "you open them and everything falls out . . . the juxtaposition of Chicago hoodlums with Plato and Spinoza and Rousseau, and, by extension, the ennoblement of crude, new America as a worthy arena for the working out of life's great questions, formerly considered addressable only in nice, old Europe."

Bellow himself has said he has come to feel there is "something delirious" about the writing in Augie : that in its exuberance and whooping, beery-breathed, weisenheimer - wiseguy- vulgarity, "it overran its borders". But, like the New York pop artists such as Warhol and Lichtenstein a generation later, who were delighted to sully the unpolluted domain of Abstract Expressionist art with a barrage of visual offences culled from the real world - comic strips, front pages, cheap ads, modern gadgets, factory food and drink, movie stars - Bellow's special perception was that cheap language didn't necessarily have to equal cheap thinking, any more than a sonorous statement couched in the language of the academy made it necessarily worth hearing. (It is a similar recognition that has allowed Haruki Murakami, a writer completely at home with all aspects of American popular culture, to breathe new lightness and life into the Japanese novel in recent years).

Augie March is the book which famously begins: "I am an American, Chicago-born - Chicago, that somber city - and go at things as I have taught myself, freestyle, and will make the record in my own way: first to knock, first admitted; sometimes an innocent knock, sometimes not so innocent." It is a sentence to which DeLillo pays conscious homage in the opening lines of his own monumental Great American Novel, Underworld (1999) - "He speaks in your voice, American, and there's a shine in his eyes that's always hopeful" - and one which has echoed, with the volume of the bluster sometimes up and sometimes lowered, the testosterone level constant between maximum and off-the-dial, in most of the zeitgeist-chasing American fiction, from Thomas Pynchon to Jonathan Franzen, via Robert Coover and EL Doctorow, that has been written in the past 50 years.

If Augie March is the first major novel knowingly written in American rather than English - if its job is "to make you feel how beautiful American is", as Martin Amis has fairly maintained, with its fearless juxtaposition of vulgar slang and the High Style - that can partly be explained by the fact that Bellow started work on it while he was on a Guggenheim fellowship in Paris in 1948. Bellow hated Paris and the grim view of post-war life taken by the European modernists - the "Wastelanders", as he called them. "I was terribly depressed," Bellow later said. The more he hated France, the more he loved America and in particular his home city of Chicago which, in the kind of "vividness fits" he would ascribe to his character Albert Corde in a later novel, The Dean's Decem ber , he started to write into existence.

It was the American critic Philip Rhav who made the celebrated division of American writers into Palefaces (those oriented to the European and specifically English literary tradition) and Redskins (those trying to create a distinctly American literature "on native ground"). And it has been forcibly argued (by David Lodge, among others) that the original Redskin writer wasn't Bellow but another Chicagoan, Ring Lardner, who, in a book called You know Me, Al , published in 1916, first showed other American writers how to get the American vernacular down right.

But as an ex-patriot living in Paris, it was the vernacular - common American - that Bellow was missing, and becoming increasingly desperate to re-connect with. Interestingly, speaking at the Guardian Hay Festival in the summer, DeLillo admitted that it was this aspect of his life at home - the fall-out from the cheapened urban experience, the teeming world of popular culture, the round-the-clock welter of visual and verbal blather - that he had most missed when he was living in Greece for a number of years in the late-70s and that it was the need to be put back in touch with everyday, trashy, spoken American that had eventually brought him home. Richard Ford, for similar reasons, has said in the past that he tries to make most of his visits to this country flying ones so that the sound of "English" English doesn't have a chance to seed itself in his head in a way that the other European languages can't.

Fifty years ago, though, with paranoia about the creeping Americanisation of British culture running rampant, and the majority of the population still strangers to any ideas of fashion, complexity, or irony, everything was geared to preventing vagabond and debased American words and images from flooding these shores. In 1953 Britain was, in still significant ways, a great power and an imperial nation. The "radio hearth" featured heavily in the advertising of all wireless manufacturers, a reflection of the BBC's public commitment "to blend the maximum of wholesome brightness with the atmosphere of quiet leisure" about the home. The music industry aimed its products at the family audience. The secret of success in print and over the airwaves was to offend nobody.

Now, in the modern global culture of consumerism and technophilia, a Holly wood actress only has to say "let's cut to the chase" while presenting an Oscar, for the phrase instantly to enter the language on all continents. A Hollywood actor only has to repeat the word 'excellent' several times in a movie for it to become a t-shirt slogan and a logo and a brand-name tie-in. "Get over it"; "Let's not go there"; "Tsunami"; "What's not to like?" A bald-faced cartoon character goes "D'oh!" and unleashes hilarity among digital subscribers and in-transit lap-top viewers worldwide. "You don't keep up with the times," says Manny Padilla to Augie March. "The big investigation today is into how bad a guy can be, not how good he can be."

"One is hip or one is square," Norman Mailer opined four years later in his 1957 pamphlet, "The White Negro". "One is a rebel or one conforms, one is a frontiersman in the Wild West of American night life, or else a square cell, trapped in the totalitarian tissues of American society, doomed willy-nilly to conform if one is to succeed."

Today in the democracy of the internet, the lines are drawn along techie, rather than criminal or non-criminal, lines: one is web-connected or not web-connected, on or off the radar, in or out of the loop. One is a cyber-surfer or a print-bound sad-arse, cut adrift from the world of "enter password" and "select location", from the strobing diplopia of the news alert and the animated pop-up ad, a stranger in the land of instant messaging and "download now" and what DeLillo has memorably called "the poetry of media glut".

Nothing is more inventive or changes as fast as American slang and the jargons that daily sprout triffid-like out of specialist areas such as entertainment, sport and information technology. "And nobody," as Frank Kermode once beadily pointed out, "notices and imitates [this] more promptly than certain English writers." "Energy has a peculiar importance, perhaps especially where American male authors are concerned," he continued in a review of Martin Amis's novel, Night Train (1997), set in America. "Saul Bellow thought that 'the code of the athlete, of the tough boy', was 'an American inheritance . . . from the English gentleman - that curious mixture of striving, asceticism and rigour, the origins of which some trace back to Alexander the Great'. Nowadays there is evidence that some Englishmen are trying to retrieve their lost virtue, and the way they go about it is to imitate American energy."

It could be argued that, for a number of years in the 1970s, the most influential prose stylist in Britain after Martin Amis (and maybe even before Amis, thanks to the breadth of his readership) wasn't a novelist but a journalist. In his weekly television reviews in the Observer, which combined seriousness and erudition with a slangy, couch-potato informality, Clive James advertised the clear debt he owed to Bellow and Roth and Mailer - and also to Pauline Kael, the long-serving film critic at the New Yorker, who had earned her reputation by kicking the language around in a wise-guy, spontaneous way that was more entertaining than the vast majority of the films she was reviewing. Kael's mantle has been handed down to New Yorker film critic Anthony Lane, an Englishman who, with his slick, epigrammatic style and ring-a-ding hipster strut manages to pass (most of the time) for an American.

Talking American is a strategy the English have always resorted to when they need to jack-up a novel's vitality and give some speed and spin to prose that is in danger of lying winded on the page. (As a teenage devotee of Tom Wolfe, Gay Talese, Norman Mailer and other practitioners of the so-called New Journalism, I feel I should put my hand up here.)

For Fury, his last novel, and his first to be set in Manhattan, Salman Rushdie, not altogether surprisingly perhaps, opted for the weisenheimer vernacular. Unfortunately, he demonstrated in the process that the latest ways of talking American are not something that can simply be phoned in. Fury read like warmed-over Pynchon or DeLillo, with more than one reviewer pointing out that Rushdie's brand-name mantras - "Prozac, Halcion, Seroquil, Numscul" - were uncannily reminiscent of "Toyota Corolla, Toyota Celica, Toyota Cressida" in DeLillo's White Noise , or "Mita, Midori, Kirin, Magno, Suntory . . . the Esperanto of jet lag" in Mao II (1991).

When Don DeLillo read from the main stage at Hay-on-Wye in May there was a Sunday afternoon audience of around 2,000 and a genuine sense of anticipation. It felt like it felt in the 60s, going to see Bob Dylan. He began reading from his latest novel, Cosmopolis : "He took out his hand organiser and poked a note to himself about the anachronistic quality of the word skyscraper. No recent structure ought to bear this word. It belonged to the olden soul of awe, to the arrowed towers that were a narrative long before he was born." It is customary on these occasions for the author to read from the book he is plugging, and from the edition of it, hardback or paperback, that will be on sale in the signing tent after the reading. DeLillo, though, was reading from loose sheets of paper. "Computer power eliminates doubt. All doubt rises from past experience. But the past is disappearing. We used to know the past but not the future. This is changing."

The central character in Cosmopolis is Eric Packer, a superrich currency trader who occupies a 48-room, $104m penthouse apartment, complete with shark tank, lap pool, and a special pen for his Borzois. Packer has had his limousine "prousted" - "I sent word that they had to proust it, cork-line it against street noise" - and the novel tracks him in the course of a single day when he takes a book-length trip across midtown Manhattan. It is a short book, shorter than the novel which preceded it, The Body Artist, which itself was considerably shorter than the remarkable "Pafko at the Wall" section which opens Underworld. It is dense and compacted, almost like concrete poetry. DeLillo read on. "It was shallow thinking to maintain that numbers and charts were the cold compression of unruly human energies, every sort of yearning and midnight sweat reduced to lucid units in the financial markets. In fact data itself was soulful and glowing, a dynamic aspect of the life process. T! his was the eloquence of alphabets and numeric systems, now fully realised in electronic form, in the zero-oneness of the world, the digital imperative that defined every breath of the planet's living billions. Here was the heave of the biosphere."

DeLillo's face flickered in close-up on a large screen on the stage behind him. He was wearing a Brooks Brothers button-down, a v-neck sweater, a professorial houndstooth jacket. DeLillo is 67 now, fit-looking and trim, probably a jogger. His hair is lustrous and his face is deeply pocked, possibly dating back to when he had chickenpox in the Bronx as a child.

These stray thoughts shouldn't have been intruding, but they were because, although it was a pleasure to be in the same room as Don DeLillo, and although the words he was reading were smart, beautifully put-together ones, they were just words - not words telling a story, or describing any kind of emotion, just unspooling words, abstract, drifting on the air like a piece of free-form jazz. Or - the criticism most consistently levelled at DeLillo - like the dream-language of a Cyborg; "cold" and "heartless" like a computer.

In his defence, it has been argued by the American academic Michael Valdez Moses, that "the technological understanding of the world, what Heidegger calls the 'essence' of technology, is so deeply ingrained in the minds of DeLillo's characters that it comes to seem unremarkable, merely the necessary expression of the way things are". Valdez Moses goes on to quote a character from DeLillo's brilliantly astringent (and very funny) but untypical "domestic" novel, White Noise : "You know how I am. I think everything is correctible. Given the right attitude and the proper effort, a person can change a harmful condition by reducing it to its simplest parts. You can make lists, invent categories, devise charts and graphs . . . I'm not a very ingenious person but I know how to break things down, how to separate and classify. We can analyse posture, we can analyse eating, drinking and even breathing. How else do you understand the world, is my way of looking at it."

DeLillo, like his immediate contemporary Thomas Pynchon and, before Pynchon, Vladimir Nabokov, has always been a cerebral, concept-driven writer, and experimental in a sense. He belongs to the generation which produced the metafictions of William Gass, William Gaddis, Robert Coover and Donald Barthelme. Sometimes surreal, sometimes parodic, these were invariably rebarbative, wilfully "difficult" texts, each trying to establish an avant-garde position out beyond realism. One of the most highly regarded of them, the proto-postmodernist John Hawkes, said, "I began to write fiction on the assumption that the true enemies of the novel were plot, character, setting, and theme." The metafictionists' formal concern was with language - words and phrases and sentences simply as sources of sounds or as spatial objects or sometimes as nonsense - and with ideas.

The intellectualisation of American fiction which started in earnest in the 1970s has gathered pace in recent years and, in the case of a younger generation of writers that includes Geoffrey Eugenides, William Gibson, Jonathan Franzen and Richard Powers, has resulted in big, brick-like novels which also double as encyclopedias. The jumping-off point for Bellow and his contemporaries was that American life was chaotic, fragmented, random, discontinuous; it was about sensory assault; it was about bombardment. A boffin-writer like Powers is willing to pump up the sense of discontinuity and chaos by homing in on life's particulate elements in the expectation of making connections and forging patterns whose existence nobody suspected before.

Powers' 1991 novel, The Gold Bug Variations , for example, seems to suggest that Bach's use of four notes in the Goldberg Variations, the four nucleotides in DNA and the tetragrammaton, the four letters in the Hebrew name of God, are all connected in a way that sheds light on our understanding of what it means to be human. The Time of Our Singing , published earlier this year, is about classical music -specifically, lieder - American race riots and Einsteinian temporality.

And Powers isn't alone in processing and incorporating vast amounts of difficult data. In Middlesex , Eugenides posits an analogy between the ancient and modern visions of destiny, while lecturing on genetics and the automobile industry. In The Corrections, Franzen references Lacan and meditates on everything from restaurant management to the post-Cold War instability of the Baltic states.

What all these novels tend to have in common is that the people in them risk becoming barely corporeal cerebral entities: there is no character who is securely there in a traditional sense, that is to say, a character with whom the reader can identify. Abstract concepts result in tundras of dead abstract language which, having so busily foraged for, the writers are reluctant to toss away. The hunt can all too often lead to a fever of what, in Pattern Recognition , William Gibson identifies as "apophenia - the spontaneous perception of connections and meaningfulness in unrelated things'"

"It is too full of language, even as the nouveaux riches are too full of money," Norman Mailer wrote of The Corrections . "Franzen is an intellectual dredging machine. Everything of novelistic use to him that came up on the internet seems to have bypassed the higher reaches of his imagination - it is as if he offers us more human experience than he has literally mastered, and this is obvious when we come upon his set pieces on gourmet restaurants or giant cruise ships or modern Lithuania in disarray."

Being a collector and disseminator of high-toned arcana is a kind of self-focusing activity which can bring more pleasure to the teller than to the told. It leaves the writer connecting with himself rather than looking outwards into the world.

It would be unfair to extrapolate from this that the current condition of the American novel is therefore an accurate reflection of how a deeply retrenched America now positions itself in relation to the rest of the world. A recent document circulated by the organisation Open Democracy, however, talked about "Americans' anorexic appetite" for books translated from foreign languages. It reported that, while the Bush administration had recruited prominent American writers to contribute to a State Department anthology and give readings around the globe in a campaign started after 9/11 to use culture to further American diplomatic interests, the State Department had announced no plans to bring cultural emissaries from other countries to the United States and translate their work into English.

Why does the American voice, "the American image of voice", as Harold Bloom calls it in The Western Canon , the voice that the history of the last half-century has been told in, all of a sudden sound so pale, so stale and grating? I found some of the answer in an essay by James Wood, published earlier this year in the New Republic magazine. Its title was "Can literature be simple?", and it took Flaubert and Chekhov as the twin poles of literature-as-style and literature-as-content. Flaubert, Wood wrote, "was not only a sick modern, but one who infected everyone who came after him . . . Even simplicity, after Flaubert, is no longer innocent, but is a simplicity that has become weary of congestion . . . The great artists of complexity, such as James and Mann and Proust, are always giving us a great deal - of themselves, of their intellects, of their prose, of their gathered data. But one way of looking at the simplicity of Chekhov and [the Sicilian writer] Verga is to note ! how much they subtract, how little they give us, how often they invite us to fill their bareness with our own feeling."

Two years ago, looking for a quiet place away from the incessant, pumped-up media yakkety-yak, I returned after a 30-year absence to the pleasures of the English kitchen-sink novel. "We buried my grandfather the second week before Christmas. It wasn't cold, but there was a light drizzle and all of us had come in thick clothes. My mother and I shared an umbrella."

Arthur Seaton, Jane Framsby, Arthur Machin - they are the kind of names Martin Amis derides in his essay "The Moronic Inferno". "Can these people really exist, in our minds or anywhere else, with such leadenly humdrum, such dead names?" He compares them unfavourably with other names - Kotzie Kreindl, Wharton Horricker, Murphy Verviger, Oedipa Maas - from the fictions of Bellow and Pynchon, but I decided I liked them.

I came across something Jonathan Franzen wrote in 1996 and presumably forgot. "When the times get really, really awful, you retrench; you re-examine old content in new contexts; you try to preserve; you seem obsolete . . . The day comes when the truly subversive literature is in some measure conservative."