I've come across this kind of comment elsewhere, and the recommendation was that "the book" is Designing Games by Tynan Sylvester (the author of Rimworld)

https://tynansylvester.com/book/

Haven't read it yet myself.

I'd say there's no such thing as 'the book' for game design and which you will jive with largely depends on your preferences and values around games.

Also your style. Game design is influenced by the mind of the designer. Some take a systematic, methodical approach to it. While others treat it like a painting, designing as they go from a core of an idea. And others go full ad hoc, with multiple prototypical designs until they find something that hits.

This is oversimplifying, most designers fall into a bucket of mixed styles; but the point is, no "book" will be perfect for all. Same as with software engineering, graphic design, etc.

Tynan's book is popular, but in my limited experience the first book most people recommend for anyone looking into design is Book of Lenses. Mind you I think both are worth reading. Lenses is just a more systemic and deeper dive.

I can definitely recommend it!

That's why I put it in scare quotes; personally I don't believe The Book has yet been written. There's not an Art of War for every subject yet, and game design is one of those subjects not yet mastered, at least in writing.

What about old school Chris Crawford's book "The Art of Computer Game Design"?