his is a book of lectures -- the Clarendon Lectures in English -- originally delivered at Oxford in 2001. It is a slim, academic text, bound in black cloth, with over 50 pages of scholarly notes and with illustrations that come from various editions of Ovid (the ''Metamorphoses'') and Dante (the ''Divine Comedy''), from Bosch's ''Garden of Earthly Delights'' in the Prado, from a great range of Renaissance art, the photograph of a zombie from Zora Neale Hurston's ''Tell My Horse,'' all the way to an illustration from Lewis Carroll's ''Sylvie and Bruno.'' Knowing the sprightliness of Marina Warner's darting imagination, and her learned yet witty and sometimes teasing capacity for following some great mythic subject over the centuries, one could imagine her entering the lecture hall a little like Sigourney Weaver's Ripley, tailed by the (so far) obedient yet hideous creature from all those! Alien films, dripping with scum, the fluids of birth and transformation, to say nothing of the dew of imagination's kindness.

Well, no, Oxford may not be quite ready yet for such sultry modernism. And a book called ''Fantastic Metamorphoses, Other Worlds'' (even one with Bosch nudes all over its jacket) may be reckoned to be the prisoner of Oxford's recognized traditions of intellectual history. But Warner moves with a high-wire walker's assurance, from Ovid, Bosch and Dante to James Hogg's ''Private Memoirs and Confessions of a Justified Sinner,'' Stevenson's ''Dr. Jekyll and Mr. Hyde'' and on to Nabokov's ''Lolita'' and even Philip Pullman's ''His Dark Materials.'' In addition, she makes several seductive moves toward that enormous threat to intellectual history, the movies, as if well aware that when it comes to mutating, hatching, splitting and doubling (her chosen topics on which metamorphosis works) the large screen, its savage if magical cuts and lingering dissolves, are what you might call the cat's whiskers. No, she doesn't go all that way, alas, as if some Clarendonian had warned her o! ff. (There was some talk in Britain when Marina Warner gave the Reith Lectures that she was not quite serious or academic enough, that she was dangerously entertaining and intimidatingly diverse in all she knew and enjoyed.) But the point is suggested nonetheless: in the larger consideration of imaginative transformations, those artists and scholars born on the far side of the invention of movie had hardly seen, or guessed, anything yet.

And so it has to be said that Warner writes her own fiction, as well as a range of nonfiction studies of heroic figures and subjects in myth (''From the Beast to the Blonde,'' ''No Go the Bogeyman'' and ''Alone of All Her Sex'') that have been widely read. She is a literary journalist. She does sometimes write about film -- she wrote the short book on Jean Vigo's ''L'Atalante'' (1934) in the British Film Institute series. She appears on television, and as is ever the way with freelancers who write and think for a living (just) she seems to have read and seen nearly anything you can think of. But what she offered in the Clarendon lectures is the steady cultural fascination with the essential Ovidian notion,

All things are always changing,
But nothing dies. The spirit comes and goes,
Is housed wherever it wills, shifts residence
   From beasts to men, from men to beasts, but always
It keeps on living. As the pliant wax
Is stamped with new designs, and is no longer
What once it was, but changes form, and still
Is pliant wax, so do I teach that spirit
Is evermore the same, though passing always
To ever-changing bodies.

One of Warner's abiding questions is how far such changeability is above or beyond the kind of moral qualms often associated with metamorphosis -- the kind of dangerous meddling with human nature and scientific order that haunted Mary Shelley and Robert Louis Stevenson. She doesn't take this large aside on, but surely there is at least a hint within evolutionary studies that the vast and gradual shift of forms that is always going on has no need to be burdened with value judgments -- except the single, blunt test: Will this survive? Especially when looking at Bosch, Warner sees something like fluency in the rampant, exhilarating way forms can find new shapes. This is Warner at her playful best, cheerfully deaf to the foreboding that so often accompanies the themes of doubling and regeneration.

Not that she misses the thrill of threat. She is persuasive about what a great writer Hogg is. She can see how other scenes from Bosch are riveting and disturbing: ''Not till Kafka's terrifying short story 'In the Penal Colony' has anyone imagined torment with such dark and subtle and ghastly comic ingenuity.'' She is also stimulating in discussing the light and magic shows popular in the 100 years or so before movies arrived. Here she is on De Quincey's ''Suspiria de Profundis'': ''Significantly, in the phantasmagoric opening fugue of this marvelously complex essay, De Quincey ravels up together even more tightly photography, ghosts, doppelg* ngers and natural wonders, when he includes among the modern inventions that represent, in 1845, 'the new powers of heaven and powers of hell,' the daguerreotype. He characterizes this new medium of duplication with the ominous phrase, 'light getting under harness as a slave for man.' ''

Of course, in Oxford in 2001, I assume, these lectures would have been heard by art historians, classicists, medievalists, intellectual historians and so on, and doubtless many of them were dazzled by the range of reference. This book will allow the slower reader more time to digest that range, as well as the piercing, playful use of ideas. But it will probably not draw smart lay readers -- people like Warner herself. So the book will probably be shelved as ''academic'' when actually it is in love with complicated but deeply suggestive and often beautiful ideas that have flowered violently in the last 100 years.

By which I mean to suggest that I would love to have a richly illustrated book by the same Marina Warner that asks us to see the unfolding of metamorphoses in the age of movies, advertising and PlayStation. For every child nowadays does metamorphic exercises for hours every day, and every parent is torn between woeful moralizing and being swept away by the wild beauty.