Caryl Phillips's The Lost Child is many things, but more than anything else it is the story of Julius Wilson and Monica Johnson and what happens to them and their children.

Monica, a slightly weird although abundantly talented girl from Yorkshire, rejects her parents and while at Oxford in the 1950s meets and begins living with Julius. He's from an island nation bent on eventual independence. Monica's father, Ronald, a fearsomely uptight, neurotic schoolmaster, disowns her (on many levels this is a novel of the buttoned-up versus the unbuttoned). Monica drops out. When Julius begins working as a teacher, they move from Oxford to the dreary south coast, and then to London, in a really depressing, vividly re-created England of the Fifties and Sixties. Julius eventually gives up his job to campaign full-time for the freedom of his birthplace. He then decides to go back there to teach, but Monica is tired of him and "his boring talks about the future of his nonsensical stupid country". She takes their two sons, Ben and Tommy, back to Yorkshire.

Living on an estate in Leeds, Monica works at a branch library, and Ben learns how to steal. Tommy drifts into a football fantasy life, and though he's brilliant at the game, his poverty and unworldliness lead to his, and his mother's, undoing. She has a nervous breakdown. Ben is left in a foster home; despite his necessary taste for larceny, he studies hard and is bound for university.

The Lost Child actually begins, however, with an exotic fable: a poor woman exploited in the Indies and then taken elsewhere, to lead a sad existence in an inn. A kindly man takes an interest in her. They have a child. You spend a lot of time trying to figure out who this child is. Could it be Julius? Julius's father? There's a kind of Steinbeck style to this: earthy but coy. The woman's story is mainly concerned with her life after the Indies, but where? (Turns out it's Liverpool, but described in such a wild, degraded manner that you think you're still in the tropics, England having brought its own savagery home.) You may or may not discern where this is heading, but be aware that the irritation of authorial vagueness is a small part of the experience of The Lost Child.

For a book really to be a novel, language has to be exemplified, twisted even. In this important sense The Lost Child is fascinating. The atmosphere and language are intricately done, shifting with the decades and locales in a kind of linguistic odyssey, a giant exercise in Fifties, Sixties, and Seventies talk, going from very male, arm's-length measured prose (the way Monica's father thinks) to the sillinesses of Oxford, the loucheness of London and the abyssal utterances of Leeds, a city for which there is not an iota of love lost-indeed the chapters of Monica's, Ben's and Tommy's story that take place there seem like a different novel entirely.

In a long chapter called 'Childhood', Ben narrates the story of his adolescence against a background of pop songs, everything from George Formby to David Bowie and Pluto Shervington. But we're never told how or when Ben could be writing this, and the connection to the music becomes looser with each vignette. Phillips is not convincing as Ben, which is surprising, as otherwise he is a good ventriloquist. It's a little diversion into Nick Hornby Land, which doesn't suit the overall tone or logic.

Something pretty peculiar happens. Breaking in on Leeds is a short, suitably wild, fictional surmise on Emily Brontë's death. (We know that Monica is interested in fiction - early on we're told what does and doesn't interest her; later we learn that the only worldly thing she leaves behind is an envelope full of diaries and stories.) Maybe The Lost Child is not necessarily a novel, but stories about (and possibly by) Monica, and about lost children, one of whom just happens to be Heathcliff. The Brontës were lost children, too, of course. All of them.

Perhaps this is the scheme: Monica realizes she is losing touch with reality. She 'channels' Emily's illness, and, deranged herself with grief over Tommy, feels she knows what the author of Wuthering Heights was fantasizing about her beloved little hero as she died. But if you really wanted to write Heathcliff's backstory, why do it in two short chapters possibly written by someone losing her mind? Because, in Phillips's view, there is much more to say. Heathcliff's resonant story is only one representation of the book's major theme, that of the 'intrusion' of blacks into Britain, wonted or unwelcome, then and now: Heathcliff, Julius Wilson, Tommy and Ben-lost. The British response to them echoes down the generations, and keeps on echoing.