I don't mean a 1.500 Linux Bible book, but a simple tutorial book to master Linux commands. Even if you have a licensed cpanel on your VPS you need to know to manage it by SSH one day or another.
How a 100 pages book can hurt making money activity?
Lucky you if you don't need.
webmasters all the time get wrapped up in trying to take care of their own server and it does hinder their ability to make money if they are constantly worrying about their server. There are hosting companies that take that worry out of your life, and the only thing you need to worry about is uploading your content.