CompTIA Linux+ Guide to Linux Certification
Jason Eckert
Math Adventures with Python
Peter Farrell
Essential System Administration
Æleen Frisch
Python 3 Object-Oriented Programming
Dusty Phillips
CCNA Certification Practice Tests
Jon Buhagiar
Cryptography Engineering
Niels Ferguson & Bruce Schneier & Tadayoshi Kohno
Unauthorised Access
Wil Allsopp