George and Sam
by Charlotte Moore
252pp, Viking, £16.99

Not Even Wrong: Adventures in Autism
by Paul Collins
245pp, Fusion Press, £15.99

What would you do if you'd lost your seven-year-old son in a strange town? Call for him? Rely on him to ask someone the way? Not if that child were Charlotte Moore's son Sam. He does not respond to his mother calling his name. He is unable to communicate with strangers. His sudden disappearance on a visit to Hereford Cathedral is one of many episodes in Moore's book that shows the sheer energy needed to look after an autistic child. Sam is picked up by a woman who finds him dancing obliviously on the banks of the Wye and lures him to a nearby newsagents. He has been similarly "saved" by passers by on numerous occasions.

George and Sam describes Moore's life with her two autistic sons, George and Sam, and her non-autistic son, Jake. Given the need constantly to watch over them, and the years of sleep deprivation she has endured, it is a miracle that she has written a book at all. With sparkling clarity she takes us through her family and personal history. She is what doctors term a "good historian", someone who recalls events accurately and understands which details might be significant and which red herrings.

Moore looks back into her sons' family histories to try to uncover any genetic legacy of unusual behaviour. As in every family, there is no shortage of material. I particularly liked her story of her paternal grandfather, who appears to have had extreme food fads: "He abhorred fat of any kind, and couldn't bear people to eat butter or cheese anywhere near him ... 'In 1898,' he remarked, 'I ate an apple that I almost liked.'"

This same man also wrote baby books about each of his four children, recording details about their idiosyncrasies as well as their height and weight. This was a family tradition that Moore was to follow. She includes excerpts from her own sons' baby books, in which she retrospectively traces the first inklings that there might be something different about George and Sam. These books provide a useful record of how Moore perceived her sons, before her thoughts were affected by her sons' diagnosis.

George had exceptionally early milestones as a baby. He smiled at three weeks, laughed at one month. He sat at five months, crawled at six and stood alone at seven months. He was hyper-vigilant and slept very little. George had an amazing capacity for learning by rote and could recite poetry before the age of two. It was easy for his parents to assume that, rather than having a problem with communication, their son was unusually intelligent and resourceful in his use of language. It was only later that Moore realised that George's language consisted principally of quotations, which cloaked his real communication difficulties.

Sam was an easy-going, placid baby, quite different from George. His speech and behaviour were odd, and he was strangely indifferent to adult company. He sought less attention so that his problems were not picked up until he was four and a half. It was after this that he experienced a devastating regression in skills, what Moore calls "his crash". With his long bouts of screaming, Moore describes him as unreachable at this time. The manifestation of autism was so different in the two boys as to make it hard to appreciate the fact that they both had the same diagnosis.

There is plenty of good advice for health professionals in this book. There is also a useful section on how to help your friend who has an autistic child. Yet, its didactic purpose aside, what makes this book stand out from others along similar lines is that it is outstandingly well-written. Moore has the ability to observe her sons closely, and lovingly to comment on their differences. She is not the first mother to have had two autistic sons, followed by a non-autistic child, but she has the literary and intellectual gifts to write a powerful and deeply affecting book about them.

As she says, she wrote George and Sam "not to bewail the 'loss' of the 'normal' children they were never meant to be, but, despite the problems, to celebrate them for what they are". Moore has written a vivid appreciation of her children, conveying her enjoyment of life with them as well as telling us about the more hair-raising aspects of her family life. This is a love story as well as a case history.

Another parent writing about his autistic child is Paul Collins. His title, Not Even Wrong, refers to a remark made by the theoretical physicist Wolfgang Pauli. He used the phrase as a put-down for people who understood so little of a problem in physics that their answers were irrelevant. Similarly, autistic people entirely fail to respond in expected ways to social cues.

Collins developed a fascination with the story of Peter, the Wild Boy, a feral child attached to the court of George I. He tells the story of Peter and a number of other prominent people over the centuries who may have had autistic traits. These accounts are interwoven with his personal history. While he became absorbed in Peter's life, his own two-year-old son was diagnosed with autism and began an early intervention programme to assist his communication and social skills.

The most interesting part of this book is Collins' self-scrutiny and his close observation of his little boy, Morgan. Again, as in Moore's book, the moment of diagnosis is engraved on the writer's memory. For anyone who makes such diagnoses professionally, hearing its effects from the other side is salutary.

· Harriet Stewart is a psychiatrist.