Twenty years ago, Candia McWilliam was a young novelist feted for her talent, her beauty and a private life that involved being adopted as a teenager by one aristocratic family and marrying into another, which she then left for an Oxford don, before leaving him for the Labour arts minister Mark Fisher. If this makes her sound like a modern Becky Sharp, her descent has been more savage than anything described by Thackeray. This, her fifth book, has a fascination beyond that of social gossip. What she calls "an unself-help book", it is composed of many layers of past, present, memory, thought, observation, query and, occasionally, opinions about fiction. It is beautiful, harrowing and in every way remarkable.
Her mother committed suicide when she was a child. Her father, a distinguished Edinburgh architectural historian, remarried to a Dutch woman who imposed a regime of diet and exercise on the fat, tall, bookish child, but gave little affection. Sent away to an English public school, McWilliam was, like many abused and deprived children, successful at finding herself alternative families, in particular a lasting schoolgirl friendship with the Howards. She won the Vogue talent competition at 16, a place to read English at Cambridge, and then a First, but "never knew that I was, sometimes, beautiful". Abnormally fearful, strikingly attractive and living in a circle of rich friends, the young Candia (or Claude, as her friends call her) was predictably vulnerable to exactly what was worst for her. She married the heir to an earldom, Quentin Wallop, by whom she has a son and a daughter, and then the Oxford don Fram Dinshaw, by whom she has another son.
Half the book takes us to this point. The second, happy marriage seems marred only by the Dinshaws' Parsee beliefs and a mother-in-law who eventually made little effort to conceal her loathing of McWilliam. Every "disobliging" review of her novels (all of which won prizes) was sent to the in-laws. However, the union was also cursed by McWilliam's alcoholism. It is this, as much as the onset of blindness, that preoccupies her in the second half of the book.
Her descent, which included leaving Dinshaw for Fisher, sounds like hell for all concerned. She describes how she drank not just booze, but "household cleansers, disinfectant, a substance called Easy-Iron", dislocated her children's lives and broke the heart of the man she still loves. Her descriptions are frank ("You shit blood. You piss blood"), but she shields the others in her life by blaming herself. Anyone who has, as I have, bought and admired her fiction from the start can't help but sorrow for the mess and loss. If nothing else, McWilliam's memoir suggests how toxic it is for any artist to live a life in which a particular form of snobbery is enmeshed with a creative sensibility - and you don't have to be a snob yourself to suffer from its poisonous effects. Clearly, the image she projected as a fashionable darling of the literary world was at odds with the emotional truth of her life, in which she sees herself as a monster, a giant, a "fat ghost".
Worse was to come when her eyelids refused to open while she was reading for the 2006 Booker Prize. What sounds like a bad joke was blepharospasm, a form of blindness in which the eye functions but the brain refuses to let it see. Her sufferings, and her attempts to alleviate her dependency, would have brought many to suicide. Paradoxically, her mother having killed herself has made McWilliam more attached to living.
Her partial, painful powers of observation never desert her, though you long for her to discover the liberation of defiance, insouciance and robust laughter. These, however, are Augustan attitudes to life, not mandarin ones. Like Virginia Woolf and Sylvia Plath, Cyril Connolly and Anthony Powell, she is not only a consummate stylist, but very funny; far funnier than her novels ever showed - although, unlike them, her humour is without unkindness. Ironically, many of the doctors and therapists she sees, instead of addressing her blindness, talk about their own literary ambitions.
But writing saved her. An account of her affliction caused a reader of the Times to contact her about a pioneering operation to peg the eyelids to the brows, using tendons harvested from the back of the legs. It was a success. As in a cruel fairy tale, she is returned to us - broken, mended, blind yet unblind, but able to see and "to attest to the goodness of life".
What to Look for in Winter: a Memoir in Blindness
Jonathan Cape, 496pp, £18.99
Amanda Craig's latest novel is "Hearts and Minds" (Abacus, £7.99)