“The Linux Command Line” by William E. Shotts, Jr. is available in pdf format for free. This book is for new Linux users who have migrated from other platforms. Most likely you are a “power user” of some version of Microsoft Windows.
This book is a broad overview of “living” on the Linux command line. Unlike some books that concentrate on just a single program, such as the shell program, bash, this book will try to convey how to get along with the command line interface in a larger sense. How does it all work? What can it do? What’s the best way to use it?