The books I'm currently reading:
1. BASH Guide
The guide is targeted at beginning users. It assumes no advanced knowledge - just the ability to login to a Unix-like system and open a command-line (terminal) interface. Familiarity with the fundamental Unix tool set, or with other programming languages or programming concepts, is not required, but those who have such knowledge may understand some of the examples more quickly.
2. Certified Ethical Hacker Version 8 Study Guide
This Sybex study guide is perfect for candidates studying on their own as well as those who are taking the CEHv8 exam. It covers all the exam objectives with an easy-to-follow approach.