Process of Network Security, The: Designing and Managing a Safe Network by Thomas A. Wadlow
Information Security Management Handbook (3rd, 4th and 5th Editions) by Tipton and Krause
TCP/IP Illustrated by Stevens
The CERT Guide to System and Network Security Practices by Allen
Network Intrusion Detection by Stephen Northcutt et al.
Inside Network Perimeter Security: The Definitive Guide to Firewalls, VPNs, Routers, and Intrusion Detection Systems by Stephen Northcutt et al.
Computer Forensics: Incident Response Essentials by Warren G. Kruse, Jay G. Heiser
Firewalls and Internet Security: Repelling the Wily Hacker by William R. Cheswick et al
Information Warfare and Security by Denning
Computer Security Handbook, 4th Edition by Seymour Bosworth, M. E. Kabay
Writing Information Security Policies by Scott Barman
The Cuckoo's Egg by Cliff Stoll
Hack Attacks Encyclopedia: A Complete History of Hacks, Cracks, Phreaks, and Spies Over Time
by John Chirillo
Practical Unix & Internet Security by Simson Garfinkel and Gene Spafford
The Code Book by Simon Singh
Security Warrior by Cyrus Peikari, Anton Chuvakin
Managing Security with Snort and IDS Tools by Cox and Gerg
Intrusion Detection with Snort by Rehman
Hacking by Jon Erickson
Hacking Exposed
Linux Server Security by Michael Bauer
Anything at the
SANS Reading Room
Joined Yahoo mailing list of other "CISSP elects" to ask questions of others.
Articles in Sys Admin Magazine
Cert Specific Stuff:
All-in-One CISSP by Shon Harris
Office ISC Guide to CISSP by ISC(2)
The CISSP Prep Guide, 2nd Edition by Krutz
CCCure Website (free testing engine)