I read this on a recommendation from a post in Mathematics Under the Microscope (now available only from a monthly archive in the Wayback Machine). It’s an account of Leo Marks’ experience working as a cryptographer during the Second World War.

The book is absolutely as gripping as any novel I’ve recently read, proving to me that I should delve into nonfiction (non-mathematical non-fiction, that is) more often.

The end of the book wasn’t completely satisfying, but this I can forgive, since the book recounts true events, and life isn’t always completely satisfying.