In the Blood, by Andrew Motion

There is something a little Jane Austenish about the world of Andrew Motion's childhood memoir. "Mum thought Hall Barn was blissful, and we agreed about that too; it was Queen Anne, she said, and the home of granny's friend, Lady Burnham." There are visits to neighbours and country-house games, a constant understory of hunting, shooting and fishing, an ever-present sense of social distinctions and the need to make the right signals, the loo-not-toilet, don't-say-beige world of the minor English gentry.

For that class and time, the Motions lead strikingly ordinary lives: dad a brewer and a Colonel in the Yeomanry, mum at home, a rider and lover of dogs, hardly a book in the house but a strong sense of decency, a grumpy old gardener, money to go to Harley Street when Andrew's knees pack up, a Daimler and a less sick-making Hillman, horses in the yard, some land with a bit of wood, an unaccountable decision to send the two boys to a prep school of archetypal cruelty, and then Radley, which was kinder, and where, through a generous teacher, the teenage Motion found poetry.

It is a tale of ordinariness, neither sanitised nor satirised. But the world these externals enshrine is far from robust. Motion's childhood is a tender and delicate thing. He is a nice boy, uncertain, shy, a little weak and vulnerable to bullies. His father is an upright and dignified man but can be terse and tense, jittery, difficult.

Talk in the Motion house does not consist of long conversations but sudden verdicts. Only on holiday does Andrew notice that his father's hair, like his own, is naturally curly. In the working year, the bulk of the time, Colonel Motion oils it to keep it flat. This emotional removal means that the father scarcely emerges above the surface. His presence here is as marginal as it must have been in life. He and his children never touch.

The book and the childhood are both really about Andrew's mother, Gilly Motion. She is like its DNA, present in every pore and limb. The young Andrew adored her and the writer continues to love her memory with both pain and tenderness. At times, nurturing young animals, loving her dogs, she is Madonna-like. The result is a hymn to familial love. But it is not a simplified picture. The method is miniaturist, evoking meaning from the tiniest of gestures, finding epiphanies in moments of unspoken desire and regret.

As the young Andrew brushes his mother's hair, "everything was doubled in the main mirror in front of us, multiplied over and over in the smaller ones on either side. Her face and mine. The powder box and the scrumpled tissues. The lipstick with its wet-looking red tip. The scent bottles with their gold labels and French words and glittering tops. They made me think the dressing table went on for ever, with its photographs trapped and smiling under the glass skin."

Moments of such vivid, suppressed and near-Oedipal intimacy recur so powerfully that one can feel almost embarrassed to be in the room with these people, as if looking at the page were an intrusion and presumption. That sensation is heightened by the pervasive sense that the family itself doesn't know what is going on. The grief and secrets of the adult world, the incommunicability of meaning within a family, the concealed truths, the half-understanding between grown-ups and children - all contributes to the feeling that the members of this family, occupying the same house, are only half-present in each other's lives. There is always something more for them to know, they never quite know it and yet we somehow do.

Motion's writing is filled with the eloquence of the detail. "Dad went on staring, his breath like a miniature sea rushing in and out." "I am on the other side of saying goodbye." "It looked as if the light on the landing was solid, like a sheet, and so she disappeared as soon as she reached it." These moments of heightened rhetoric, in a way clearly reminiscent of Philip Larkin's poetry, are set against a background of slanged-up language, more like what the teenage Motion would have said himself. "All the other mums weighed a ton," he says of an open day. When he is ill, Mum is always "wheeling the telly in". "She was standing at the head of the table," he says of her at one point, "with one hand on her hip, and the other holding a battered spoon. Like a fat cook in a picture, except she was so thin the light from the stable yard shone straight through her."

This dialogue between then and now, between the man who sees in retrospect his mother's utter fragility and the boy who saw her standing there like a funny fat cook, is a way of dramatising the coexistence, which is perhaps the book's ultimate subject, of significance and insignificance, the ordinary meaninglessness of lives and the sense of nearly overwhelming meaning those same lives can have when remembered after they have gone. His mother is a funny cook; but she's a loved mother and a dead one.

That sense of loss governs page after page. For all the immediacy, these are unrecoverable moments. And their vividness was all too fragile at the time. Motion's childhood seems to have been full of threat: not only cruelty from a school teacher (the "dark red tip of his tongue kept appearing like a lizard's, licking the edge of his moustache. It made him look as if he were eating flies"), but from life itself. Penknives fall through cracks in the floor, never to be found. Stacks of hay threaten "to make you strawberry jam". The Christmas present of a decanter breaks at the moment it is to be unwrapped. "Why was mum ill so often... Maybe things weren't safe after all."

The story is framed by catastrophe. When Motion was 16, as he was kissing a girl in some other part of the county, his mother fell from her horse when out hunting. She hit her head on a concrete track, did not recover consciousness for three years and was never the same before she died six years later.

In the Blood begins with a description of the day of the accident and ends with the day on which Motion and his brother see their mother for the first time in a coma. Both chapters are disturbingly powerful accounts of disaster, grief, denial and realisation. The dreadfulness of what they describe exists on another plane from the smaller, carefully drawn triumphs and disasters. But the framing chapters justify the whole: the savage loss is the fuel for the insistence and detail with which the memories of this childhood have been recovered. If his mother had not been destroyed by her fall, where would the need have been to remember her as intensely and painfully as this?

Adam Nicolson's 'Men of Honour' is published by HarperPerennial