As so much of Alan's posthumous fame is for cracking the naval enigma in WW2, I'd recommend starting out by first reading "The Code Book" by Simon Singh for general background.
Personally I find Alan's work on ACE the most fascinating. Sadly I can't really find much about it beyond Hodge's biography. Anyone got any good leads re ACE?
I stopped reading the "Alan Turing: The Enigma" by Andrew Hodges yesterday. It's extremely detailed, like reading an encyclopedia more than a novel. I think that large chunks of the book are absolutely impossible to understand for people who do not have at least some familiarity with cryptography and mathematics.
But if you are interested in the ins and out of Turin's life it's a very good reference.
I don't remember it having any difficult parts, but I did read it over 10 years ago so maybe I am mistaken.
I'd encourage you to go on with the book; it's a beautiful book. You can skip over the overly science-y parts I guess. The beauty of that book in my opinion is how the author didn't focus solely on his homosexuality or achievements but tried to show how his personality, including his sexual preferences, played a part in everything that he was able to achieve.
Not a book but I would recommend watching 'Breaking the code' a BBC play from the mid 90's about Alan Turing starring the ever excellent Derek Jacobi. It can be watched for free on youtube here [https://www.youtube.com/watch?v=S23yie-779k]
Slightly off topic. If you're ever near Washington, DC, there's a working enigma machine and a non-working USA version of the enigma cracking bombe at the National Cryptologic Museum near the NSA HQ. I was there yesterday, and thought it was pretty interesting.
1. Alan Turing: The Enigma by Andrew Hodges http://www.amazon.com/Alan-Turing-Enigma-Inspired-Imitation/...
Definitive and detailed biography.
2. Alan M. Turing by Sara Turing http://www.amazon.com/Alan-M-Turing-Centenary-Edition/dp/110...
Deeply personal biography of her dead son.
3. The Annotated Turing by Charles Petzold http://www.amazon.com/Annotated-Turing-Through-Historic-Comp...
Turing's famous 1936 explained in detail.