Following books are available

linux (.pdf)
linux-sistem-yonetimi (.pdf)
Network_Scanning_Techniques (.pdf)
Securing-Optimizing-Linux-RH-Edition-1_3 (.pdf)
bash
High-Performance_Networking_Unleashed
Linux_System_Administrators_Survival_Guide
LinuxSystemAdministratorsSurvivalGuide
Maximum_Security
Red Hat Linux Unleashed - more graphics
Red_Hat_Linux_Unleashed
UNIX Unleashed - Internet Edition - SAMS
UNIX Unleashed - System Administrators Edition - SAMS
Unix_Unleashed
Unix_Unleashed_Internet_Edition
Unix_Unleashed_System_Administrators_Edition
UnixUnleashedvisitors.