I spent a lot of this weekend reading Colossus: The secrets of Bletchley Park's code-breaking computers by Jack Copeland and others (http://www.amazon.com/Colossus-secrets-Bletchley-code-breaking-computers/dp/0199578141/), and it is amazing, so I thought I would recommend it here.
Of course, it is the story that book has to tell, rather than necessarily the way the book is written, that makes it amazing, but acutally it tells the story very well. It makes what we are all doing on Moodle seem fairly tame and inconsequential by comparison.
Of course, if you ever find yourself in the UK near Milton Keynes, you must visit Bletchley Park and see where it all happened.