Zadie Smith's third novel, her first to make it to the Man Booker shortlist, begins uncertainly but grows in stature as it goes along -- until, almost without the reader realising it, it's developed into an expansive, moving work.

On Beauty is equal parts family drama, entertaining campus novel, nuanced character study and a quietly powerful account of clashing ideologies.

Occupying the centre of its stage is the Belsey clan, who live in Wellington, a small American college town. Howard, 57, an academic with a perpetually pending book on Rembrandt, is a white Englishman, but his wife Kiki is African-American; a typical family conversation might include Howard making 'a series of excruciating hand gestures and poses' in a mock-attempt to convince his three children that he can be as 'street' and as 'brother' as any of them.

The Belsey family is already under considerable strain, Kiki having recently discovered that Howard had an extramarital affair with one of their friends. But things promise to come to a boil with the arrival in the university campus of Montgomerie Kipps -- a right-winger with whom Howard has had a long-running academic feud -- and his family.

Relationships soon intersect in a variety of combinations. The Belseys' daughter Zora barnstorms her way into the poetry class taught by Claire Malcolm, Howard's ex-lover. Their younger son Levi, after a half-hearted attempt at staging a protest at the department store he works in, gets involved with Haitian immigrants and becomes interested in the politics of injustice.

Howard finds himself teaching Monty Kipps' sexy daughter Victoria, with whom his older son has already had an ill-fated affair. And in the novel's most ephemeral but also most significant relationship, Kiki develops a bond with Kipps' convalescing wife.

Theirs is partly a story of two women finding shared humanity while their men rage about the Big Issues, but it is also a relationship founded on loneliness and mutual empathy -- and a direct echo of a similar relationship between two women in a book Smith repeatedly references: E M Forster's Howards End, about class conflicts in a very different time.

If this sounds like so much soap opera, it doesn't begin to convey the many little vignettes that add up to make this book. A magical chance meeting between the three Belsey siblings that could easily have been ruined by a lesser writer, but which Smith pulls off with conviction.

Howard's repeatedly having to run out of solemn ceremonies -- once because he's on the brink of tears, another time because he's choking with laughter. The poignance of his meeting with his estranged father -- aging, lonely, but still hopelessly racist. Kiki's explosive tirade: 'Everywhere we go, I'm alone in this� this sea of white. My whole life is white. I don't see any black folk unless they be cleaning under my feet in the caf� in your college."

A chuckle-inducing description of a mother and daughter running towards each other, 'each with her rich, strange news' (the 'news' in one case being that the father has been unfaithful yet again).

Little cracks do show up too. The beginning (with sentences like 'It was an offer to kick open a door in the mansion of their marriage leading on to an ante-chamber of misery') is awkward and it takes time for the narrative to settle down. The Kipps family seems like caricatures in an important scene where a will is being discussed.

And one sometimes gets the sense that the book was intended to be lengthier: that portions were lopped off, and entire characters with them. (There is an extended scene with Monty's son Michael early on, but we barely see him again; there is at least one character whose very appearance in this final draft is perplexing; and we don't get up close with Monty Kipps -- whose beliefs are crucial to the story -- until very late in the proceedings).

Though this stop-start effect persists throughout, it never becomes a serious impediment. This is a book that quietly creeps up on you. Close to the halfway mark, I wasn't even sure what I thought of it; by the time I'd finished I wanted to read it a second time, even wished it was slightly longer so that one got more time with the characters. In this age of tiresomely thick novels by precocious young writers jostling for your attention, that's quite an achievement.