Firewalls and Internet Security: Repelling the Wily Hacker (2nd Edition)
Firewalls For Dummies
Firewall Fundamentals
TCP/IP Network Administration (3rd Edition; O'Reilly Networking)
Linux Security Cookbook
Linux Firewalls: Attack Detection and Response with iptables, psad, and fwsnort
Blue Team Handbook: Incident Response Edition: A condensed field guide for the Cyber Security Incident Responder.
Rtfm: Red Team Field Manual
The Network Security Test Lab: A Step-by-Step Guide
Network Warrior: Everything You Need to Know That Wasn't on the CCNA Exam