Although I haven't read this book, I read its ToC. Apparently it seeks to introduce you to the Emacs way of doing things. And guess what? Near the end, it emphasizes how to use Emacs' self-documention: https://www.masteringemacs.org/book/look-inside/table-of-con...

I'm embarrassed to say how long I used Emacs knowing about C-h f -- but not noticing and using C-h i to read the full documentation from inside Emacs. I wish I'd appreciated that from the start.

At this point I've read the full Info doc at least once through, some sections multiple times. It's impressively good, especially for getting a crisper understanding of topics you only sort of understand. It's one of Emacs best features.

But I can totally see the value of a good introduction book, and wish I'd had one when I was starting out. So although I don't know how good this book is, I don't think a book is pointless.