Review: Big Brother, By Lionel Shriver

He ain't heavy ... he's obese

Lionel Shriver is famous for two things: her prize-winning novel about motherhood, We Need to Talk About Kevin, and her personal obsession with diet and exercise. Big Brother conflates the two in being about a woman's reaction to her brother's obesity.

Pandora is the middle-aged middle child in a middle-class Midwestern family, unexpectedly rich owing to her invention of a doll. She doesn't like the publicity, but loves her "big, lobotomised" house in Iowa, her craftsman husband and his two teenage children. She also loves her big brother Edison, a handsome jazz player who left their dysfunctional family for a life playing jazz in New York. But when he invites himself to stay for a couple of months, she fails to recognise him at the airport.

Edison has ballooned into the kind of fat person who overspills airline seats, gets shoved into alcoves in restaurants, eats obsessively and has opted (in one of many choice phrases) for "suicide by pie". His egomania, mendacity, dated 1950s slang and poor hygiene notwithstanding, Pandora continues to love him, even when he breaks her husband's most precious creation and blocks the toilet with gigantic turds. She cleans up, and decides to save her brother's life.

Part of the fascination of this horridly gripping tale lies not only in its upmarket rendition of Stephen King's tropes, but in its portrayal of fragile family dynamics. "What is wonderful about kinship is also what is horrible about it: there is … no natural limit to what these people may reasonably expect of you." While their television-star father is a bore, Edison is a monstrously entertaining creation, as is Pandora's over-controlled and controlling husband, Fletcher. Initially polite, he makes no secret of his distrust and contempt, escalating to a challenge: if Edison loses 58 per cent of his weight, and returns to 163lb, the health-obsessed Fletcher will eat a chocolate cake in one go.

Few subjects can be as topical as this one, and enjoyable as her novel about cancer (So Much for That) was, Shriver has written her best novel yet in Big Brother, inspired by her own brother's death from obesity. Although still prone to hectoring, she examines America's "alarmingly large underclass", in which obesity "had become a social issue on top of a personal one", with surprising compassion. The novel's journalistic tendency includes some ponderous Americanisms, but we are compensated for that by a multitude of well-chosen details about what it feels like to be fat, then thin; loved, then not.

Pandora's tale takes us on a rollercoaster ride, structured into three sections called "Up", "Down" and "Out", before an entirely literary twist at the end. Brace yourselves for some disgustingly visceral episodes – but who would have thought that a novel about a diet could be so moving, and so suspenseful?

Amanda Craig's novels include 'Hearts and Minds' and the recently reissued 'A Vicious Circle' (Abacus)