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.