Alan Turing was one of the great pioneers in the design and use of stored program computers. Generally speaking, he was brilliant but eccentric, steeped from childhood in the study of science and math and adept in the uses of those subjects. However, he was usually rather ill at ease in casual conversation.

This book was written by Turing’s mother. Thankfully, there is also a measured foreword by Martin Davis that discusses Turing’s experience as a mathematician, a wartime codebreaker, a computer pioneer, and an artificial intelligence (AI) theoretician. There is also an honest remembrance by Turing’s older brother, John, that will be received by many as the frosting on the cake.

In Sara Turing’s telling, her son Alan was a brilliant child, a vigorous long-distance runner, a fabricator of scientific instruments of his own design, and what the casual observer might call a “computer scientist.”

He was also, it seems, a person who did not suffer fools gladly, but here it should be added that he was generous with his time and wisdom to those of lesser mental skills than his who sincerely wanted to learn.

He was a mathematician and an AI theoretician. During the Second World War, he was a superb codebreaker, responsible for decoding messages sent to, from, or within the German military.

He was maddening, brilliant, unusual, and unkempt, depending on whether one accepts his mother’s view or that of his older brother. The world needed Alan Turing in the early years of computer science, and it still does.