After teaching literature at three universities in Tehran (and being expelled or resigning in despair from each) Azar Nafisi picked seven of her best students and invited them to come to her home every week to discuss books. She and her students, all women, began to think of these classes as an escape from the reality of Iran's totalitarian theocracy; but the picture her book paints is of an escape to a true republic where they are all able to discover another reality - themselves.

The classes lasted from 1995 to 1997, when Nafisi left for the United States. But why Lolita? Nafisi's choice of Nabokov as an author to study is only partly an acknowledgement of the hard, precise beauty (and sometimes difficulty) of his prose, always read in English. In her class Humbert Humbert's seizure of his nymphet's life and identity becomes a metaphor for the way the radical Islamic state was treating its women - not least in his recording that it was Lolita who initiated their sexual relationship, the adolescent who seduced her stepfather; it felt as though radical Islam was blaming women.

But the seven students who unexpectedly bonded at Nafisi's home also responded enthusiastically to Nabokov's other work and particularly to his use of the Russian word poshlust. She quotes him: "It is not only the obviously trashy but mainly the falsely important, the falsely beautiful, the falsely attractive." These qualities linking the banal and the brutal are not exclusive to totalitarian society nor even the 20th century, but they have thrived happily in Stalinist Russia, Nazi Germany and now the priestly dictatorships too.

This book is not a political or even ethical analysis. It is taken for granted that the accusation that personal freedoms are a bourgeois and decadent concept is condescending and stupid; the problem of societies where historically only the privileged have had such freedoms is not addressed.

Although Nafisi's classes start with Shahrazad and the Thousand and One Nights, the book concentrates on the western literature that has been her academic subject; references to the great Persian tradition are few, and all the more frustrating because they can be so telling.

This is a highly personal memoir combined with literary criticism, but even that description needs qualifying. The students whose developing stories are part of its pleasure have been disguised for their own protection. Moreover, in a manner redolent of the Persian tradition, she refers throughout to one confidant simply as "my magician", conveying a near-mystical sense that he is a presiding genie in her life. This may be less than objective but it releases a story that is vivid, often heroic and sometimes funny in a ghastly way.

For instance, a friend starts to translate Ayatollah Khomenei's writings into English, an activity which will gain favour with the regime while actually exposing it to ridicule. Nafisi quotes a section in which the country's leader sanctions sex with animals as a way of keeping men's appetites under control. Is it all right to eat, say, a chicken you've had sex with? No, but you can feed it to a near neighbour, apparently.

Meanwhile Nafisi and her family survive bombs and missiles from Iraq (supported by the west), and having been expelled from one university for not wearing the veil, she is persuaded by a benevolent pragmatist to adopt it so she can work in another university, on the basis that some intellectual life is better than none; but eventually she is driven out of that one too.

The charismatic passion in the book is not simply for literature itself but for the kind of inspirational teaching of it which helps students to teach themselves by applying their own intelligence and emotions to what they are reading. When the group reads F Scott Fitzgerald, for instance, there are plenty of puritanical students to argue that The Great Gatsby is a poor role model. Following the fashion of the time and place, she encourages them to put the book on trial. There are speeches for the prosecution and defence, but the only witness is the book itself - and she plays the book. She closes the class before a vote is taken, but not before the dialogue has demonstrated both the positive value of the book and the pointlessness of analysing it in terms of role models.

Perhaps the most moving section relates to Henry James's Daisy Miller, whose heroine - in telling an emotionally reticent admirer not to be afraid - embraces her own difference and fate. It is with Daisy, in the end, that her students most identify and Nafisi's rather wonderful book touches a beauty of its own.