Simon Singh's "The Code Book" is a good overview and well written. http://www.amazon.com/The-Code-Book-Science-Cryptography/dp/0385495323/ref=sr_1_1?ie=UTF8&qi

Simon Singh's "The Code Book" is a good overview and well written. http://www.amazon.com/The-Code-Book-Science-Cryptography/dp/0385495323/ref=sr_1_1?ie=UTF8&qid=1367588416&sr=8-1&keywords=The+code+book http://www.amazon.com/The-Code-Book-Science-Cryptography/dp/...