Hacking - The art of exploitation
Jon Erickson
sed & awk
Dale Dougherty & Arnold Robbins
How Linux Works, 3rd Edition
Brian Ward
Building Secure and Reliable Systems
Heather Adkins & Betsy Beyer & Paul Blankinship & Piotr Lewandowski & Ana Oprea & Adam Stubblefield
The Wireshark Field Guide
Robert Shimonski