All my recommendations happen to be mentioned on this list, so I'll mention them here:

- Stealing the Network, a collection of short stories. One of those stories was written by Fyodor of nmap and is available online: http://insecure.org/stc/ -- this sort of works like a tutorial for nmap and networking security. :-D

- Snow Crash by Neal Stephenson

- Cryptonomicon by Neal Stephenson

- Neuromancer by William Gibson