This is non-fiction as beach read, and felt more like a book-length Slate article that a serious attempt to understand or make an argument. The sources are the author's personal experience and a few interviews, so it comes off like a memoir of escaping a cult written by someone who was never in a cult.
The fitness and online influencer sections taught me a few new things, but the early parts of the book about religious cults gave high level summaries of the cults that are already the best know to any reader who has an interest in the subject.
At its worst this felt like the downscale kind of true crime or cult podcast where the hosts riff over a Wikipedia summary.
I was hoping for more depth, better research, and a clearer thesis. I would have stopped somewhere midway if this weren't as short as it was.