I was going to recommend the Hodges biography of Alan Turing, but it appears to be (sadly) out of print. http://www.amazon.com/Alan-Turing-Enigma-Andrew-Hodges

I was going to recommend the Hodges biography of Alan Turing, but it appears to be (sadly) out of print. http://www.amazon.com/Alan-Turing-Enigma-Andrew-Hodges/dp/0802775802/ref=sr_1_1?ie=UTF8&s=books&qid=1263905638&sr=8-1 http://www.amazon.com/Alan-Turing-Enigma-Andrew-Hodges/dp/08... [edit: In the US. Someone else posted the link to the UK edition, thanks!]