I have a personal interest in Cryptography, I would like to learn more about the history of it and would like to know if David Kahn is a good place to start?
I've also been eyeing off Bruce Schneier books.
The Codebreakers is good, if you're interested in stuff that's mostly not in use anymore. Schneier's Applied Cryptography would be a good companion for more modern crypto (up to about 1996).
I would also recommend Simon Singh's The Code Book and for an account into computer networks before the adoption of encryption the autobiographical The Cuckoo's Egg: Tracking a Spy Through the Maze of Computer Espionage by Clifford Stoll, which gives a very good insight into the beginnings of computer security.