Although learning to attack (and defend) is great fun, I suspect a profound understanding of the basics is essential to gaining real expertise. Not a book, but this site http://www.linuxhomenetworking.com/ is a great place to start, especially the chapter on Linux Wireless Networking.
Also bookmark http://code.google.com/p/pentest-boo.../BookmarksList


And I'm currently reading the lpic-1 study guide and the metasploit penetration tester's guide. I don't know if this is enough to start with, but if I'm missing something feel free to add something.
