Enigma, by Thomas Harris

So this has been my "car book" for the last few months. It's the book I leave in my car for when I forget to bring a book, so that I always have something to read. I've read it before, a long time ago. I read it in little chunks over a long time, but it's an engaging story about WWII code-breakers at Bletchley. Just enough math to make it interesting, without making it unreadable.