A cute idea, to present gender as a choose-your-own-adventure type journey through the infinite possibilities that exist in the universe of gender. Of course, it would be impossible to fit infinite possibilities into a physical book, so the possible pathways are pretty constrained.
The author does attempt to address intersectionality, but either because of space limitations or lack of research data, the pathways for cultures outside of the USA are pretty short, and even within the USA pathways, things like race and disability are discussed for a few pages and then the pathways merge back into the mainstream paths (something which is very noticeable when, for example, you're following a pathway about being disabled, and you get to the section talking about gender and sports, with no mention of how disability affects your ability to play sports). Similarly, although there's a lot of discussion of nonbinary genders early on, eventually you reach a point in the pathway where you've merged back into the main path, and the choices for e.g. your relationship to work are reduced back to the binary.
So it definitely has flaws. But I still like the underlying idea, and it might be a good book to open someone's eyes who hasn't thought deeply about any gender outside their own.