Learn Linux Shell Scripting – Fundamentals of Bash 4.4: A comprehensive guide to automating administrative tasks with the Bash shell

This book is pretty good about getting you up and going, especially if you are not super familiar with using bash on a Linux-based system. It starts you out by getting a virtual machine running with Ubuntu, and takes you through all the fundamentals of using bash from the simplest commands to using regular expressions and advanced shell scripting. It's more than a reference, too; each chapter has lots of questions at the end and further reading if you want to dive even deeper into the topics presented. Even a bash pro will learn something new.