If you're looking for a book on cryptography, then you'll not find anything that tops Applied Cryptography by Bruce Schneier. It's even filled with sample source code.

If you're into cryptography and hacking and the likes, a good work of fiction that's certainly worth looking into is Cryptonomicon by Neal Stephenson, the well known cyberpunk author. Snow Crash by the same author is also good.

As for books about viruses and hacking, I'm pained to say that you will most likely be wasting your money, unless you're a white collared middle-aged manager working for some mind-numbing corporation, that is. The information written in these books is geared towards that target demographic, so caveat emptor.