The pocket is perfect for beginners. It has a nice introduction in chapter 1 that explains all essential concepts to understand and operate the console. Then it is basically a sort of reference of a moderate list of most useful commands for performing different tasks.

The "Efficient" book is an in depth walkthrough of the shell and how to reason and combine important commands to perform not trivial tasks. It is certainly a book to be re-read from time to time because it has plenty of good tricks and explanations.