Cryptonomicon is a pretty shallow treatment of intelligence during ww2, and Stephenson makes stuff up (as fiction, he doesn't claim it is fact) when the truth is even more outlandish.

I would recommend the following books:

http://www.amazon.com/dp/0743217349

http://www.amazon.com/dp/006097771X/

http://www.amazon.com/dp/0679762892

http://www.amazon.com/dp/068486780X/

http://www.amazon.com/dp/0452287472

http://www.amazon.com/dp/1452206120/