Learning the Unix OS

Learning the Unix OS - 5th Edition
Jerry Peek, Grace Todino & John Strang ( O'Reilly, 2002 )

This book is now over 20 years old, yet it has aged gracefully. 
You may treat this book as a Practical Guide to Unix
Roughly 90% of the information inside is still relevant today and the other 10% can be treated as a history lesson. 
The reason can be found in the book's preface.

This book teaches basic system utility commands to get you started with Unix... We cover a commands most useful features...

And it more than lives up to its purpose. While Linux & Unix have changed a lot over the years the command line itself hasn't changed radically. The reason why the commands shown are interchangeable is that many of the core commands are identical in terms of syntax and functionality between Unix & Linux. There are of course some differences, but they are not enough to be a problem at our current level. We won't learn about Modern Filesystems or Containers, but we will learn enough to get even more confident with working through Linux.