If you buy only one cryptography book...,
Von Ein Kunde
Rezension bezieht sich auf: Applied Cryptography: Protocols, Algorithms and Source Code in C (Computer Science) (Taschenbuch)
...this is the one to buy. A straightforward read, with clear and unambiguous descriptions of crytography concepts, algorithms and implementations. Not exactly a book for beginners, though; it is clearly an intermediate text, with lots of mathematical detail (most of which was WAY over my head, but I kinda-sorta understood some of the simpler math). Schneier also goes to great lengths to insure the accuracy of the book and publishes a detailed errata on his web site.
I'm looking forward to the 3rd edition already...