BOOKS: FICTION: Secrets that eat into the soul

Childhood memoirs can be coy, pretending to know less than they do and cutely allowing the reader to fill in the gaps. One of the strengths of Reading in the Dark, Seamus Deane's marvellous memoir, or novel, about growing up in Derry in the 1950s, is that it is frank about what it knows and what it doesn't. It honours the immediacy of a child's vision without being fey or faux-naif. It's written in the past tense, and we're always dimly aware of the easel of the adult artist as he portrays the young man.

There's a fine chapter near the beginning, in which a traumatic episode is observed from under the kitchen table, where the boy narrator sits with his whimpering collie. Ambulancemen have come to stretcher away his sister, Una, who has meningitis. We follow the drama in the movements of adult feet: the grieving father in his scuffling workboots; the shiny black shoes of an ambulanceman, which have "a tiny redness in one toecap" when he puts the stretcher down on the linoleum; the father standing to hold and comfort the "cough-crying" mother, whose feet are swollen and whose low heels need mending; the shape and pain of their embrace - her shoe, then his boot, then her shoe, then his boot. The narrator is enough of a child to tell us, impiously, that he loves the names of illnesses (diphtheria, scarletina, rubella, influenza), which make him think of Italian football players or racing drivers. But he also lets us know that Una is going to die, and is mature enough to feel not just the blade of his own distress but the weight of his parents'.

How a child can come to be burdened with adult knowledge is the theme of the book. Early on, the narrator is relatively passive and protected - an eavesdropper on the grown-up world. Magic and folklore swirl around. His mother speaks of the ghost in the landing window; his aunt tells him stories of possessions and metamorphoses and sleeping warriors; he learns how if you meet somebody with one green eye and one brown you should cross yourself, "for that was a human child that had been taken over by the fairies"; he visits a field no gulls will fly over, the Field of the Disappeared. Even Derry, gauzed in smoke, a city of bonfires, the border writhing behind it, seems part of this Faeryland.

But Part Two of the book begins ominously, with a brilliant description of men and dogs working together to drive a plague of rats from the neighbourhood. The mood is graver now, the city a sectarian Hamelin. Half-grasped fragments of family history - the disappearance of an uncle, a feud involving the shocking mistreatment of two aunts, an IRA shootout with the RUC way back in 1922 - assume a dark but distinct shape, an heirloom of guilt that's part of a larger story of tribal conflict. There's talk of informers. Even the narrator is accused of becoming one: on the brink of being beaten up by bigger boys, he craftily throws a stone at a police car to attract attention, is hauled off in it, and apparently betrays the names of his assailants. His parents are ashamed. Friends shun him, even at football: "If I watched a game and kicked the ball back from the sideline, the player would lift the ball and wipe it on the grass before going on with the throw-in." He rebels, tries to run away, tears up his parents' rose bushes in impotent rage. Finally, he uses a clever ploy - and he is clever all right: a scholarship boy, a star pupil, a candidate for the priesthood, a reader of novels in the dark - to restore himself in the family and community.

At the same time, he is entrusted with the terrible secret of his family's troubles. It's knowledge he has courted and striven for, having already picked up enough about his missing uncle, Eddie, to realise that he holds the key. But when he learns the truth about Eddie from his dying grandfather, it's more than he has bargained for, information even his father is unaware of (how much his mother knows, he can't yet be sure). The truth seeps into every corner of his home, affecting his parents' marriage and his mother's sanity. He tries to discover every last clinching detail. But the more he knows, the more he realises this is truth too dangerous ever to tell. His relationship with his parents suffers because of it. But still (until this book), he holds his tongue.

A reviewer must hold his tongue, too. This is a book about the thrill and pain of finding out, and the reader's journey should mirror the narrator's slow climb towards the glare of knowledge. Inevitably, the book narrows as it progresses, trapped in its own obsession: a Bildungsroman to begin with, it ends up a kind of whodunnit. But the pacing is masterly. And its command and love of storytelling make questions about status - fiction or non-fiction? - look beside the point.

Reading in the Dark has the feel of a work with a long gestation: a life's work, the book that Seamus Deane - who has already published some fine poetry and criticism - was born to write. As a child, he went to school with Seamus Heaney (a graceful allusion to the fact is smuggled in here), and a Heaneyish note is discernible even in the book's opening sentence. But Deane is his own man, a city boy not a country boy, the son not of a farmer but of a man who would "sigh-heave himself out of the chair", releasing "all the salty, chalky smells of the docks that were folded into the wrinkles of his dungarees". The prose here is often lyrical and sometimes liltingly high-coloured ("scimitar slices" of tinned peaches, the "slashed light" of a window, the "squat peace" of a church), but Deane never forgets that he must also disclose hard information - some of the hardest in the world.

The Troubles of Northern Ireland have produced some memorable books. But none has shown as achingly as this how the public, headline world of murder and retaliation, rumour and set-up, silence and suspicion, can enter deep into a single family, penetrating and destroying its heart. It's desperately sad to read, and almost impossible to put down.

! 'Reading in the Dark' by Seamus Deane is published next week by Jonathan Cape at pounds 13.99