Book: The Code Book By Simon Sing

This is a pretty good book about cryptography.  It starts at mono-alphabetic substitution and ends at quantum cryptography.  The book is slow moving at some points, but in general it is fine.  It covers all the subjects in great detail.  It covers a lot of history on what provided the motivation to have the code created, and how it was created.  For every single code besides quantum cryptography, the book demonstrates a way to crack it (including public key cryptography).  Another few codes it explains are the enigma machine, vigenére square, and the Lorenz cipher.  If you like codes, this is a great book that you should read.  I had fun learning about all the different codes and I hope you do too. 
If you want to, you can get the book from Amazon here:
http://www.amazon.com/Code-Book-Science-Secrecy-Cryptography/dp/0385495323/ref=sr_1_1?ie=UTF8&qid=1318086550&sr=8-1