The jacket of Janice Galloway's memoir shows a photograph of two women and a little girl jammed together on a sofa. The older woman's lips are parted in a tense, placating smile. Her body curves towards the little girl whose pink dress spills over her own skirt. On the child's other side a young woman eyes the lens with hard, flirtatious challenge. Her fingers rest, claw-like, on her sister's lap. The child peeps at the camera from between these two mentors, her gaze submissive and secretive.

The memoir's title insists that Janice Galloway is and is not that five-year-old, born in 1955 to a mother who either genuinely believed that her pregnancy was a symptom of the menopause or more likely blocked out every sign that might lead her to an unwelcome conclusion. Names are changed a little - Janice Galloway's sister Nora is renamed Cora, for example - as if Galloway were intensely aware that a memoir is a version, a forgetting as well as a remembering, and a story in which the author is no longer a vulnerable child but an adult with the power to edit and even to erase.

If the memoir is not about “me”, then it is about a child born of a dissolving marriage and brought up by a mother who works flat-out to provide. The small, fragile family establishes a home above the doctors' surgery which the mother cleans. Routines develop; the child is biddable, silent and desperate for love. Suddenly, with a pantomime flourish, her lost sister, a generation older than Janice, appears. She has abandoned her own husband and baby - or perhaps babies - and now returns like a big, bold, marvellous cuckoo to squat in the nest and crush its other occupants.

The character of Cora is the triumph of this memoir. It is a brilliantly nuanced portrait of a woman whose gift for causing harm is as great as her fairground charisma, and who has her victim ready-made at home in Janice. Cora wants much more of life than is available to her in 1950s Saltcoats, and far more attention than can be given by an overworked mother and a wary little sister. Men are an outlet for her fearsome vitality; smoking and knitting tranquillise her fingers; elaborate rituals of dressing up for the night out assuage her furies. But whatever she really wants she does not get it, and she becomes a monster who batters and jeers at her sister as if they were both 6 years old. Cora's sudden favour is dangerous. Cora's moods must be respected as if they were the whims of the gods.

Many harsh things are said in this home, and not many kind ones done. There's little of the unthinking, tuned-in tenderness that makes a child grow in ease. It's a world where you needn't bother bringing home your report card unless you are top of the class, and where a mother says aloud the words that no child can forget: I wish I didn't have you. But the memoir also pays tribute to a a remarkable force in the Galloway family. Cora's energy could light a city; the grief is that it never will. Janice's future is foreshadowed when she puts up her hand in class to sing, because she knows she need only open her mouth and music will be there. It will take an outsider to say “You have a lovely voice”.

This is Not About Me by Janice Galloway
Granta Books, £16.99 Buy the book

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