Secret Days: Codebreaking in Bletchley Park: A Memoir of Hut Six and the Enigma Machine
I liked this book, but found it hard at times to get into. I wouldn't recommend reading it if you're tired or not focused—if it's the case, wait until a better moment. There's plenty of interesting information in it, that made me want to really peruse the matter (and add more to read to my eternally growing pile of books...); but the author tends to jump from memory to memory at times, which means that if you're not focused on his train of thought, you might get a little lost along the way.
