Yeah I have some experience with a book on Amazon. It was a great book and sold well, and often competitors would come up. The competitors were (this is pre-AI times) mostly a bunch of junk text scraped from wikipedia and the like, compiled by very low wage people out of India. From looking at the book (using the "look inside") feature on Amazon, I would often be able to spot multiple egregious errors just in the pages I was able to see, the book would often be complete and utter useless trash.

And then you'd see multiple 5 star reviews, talking about how the book changed their life. Yes, reviews are broken. Not so much on a place like Walmart, but on Amazon, you can put very little trust in reviews.

Some ways that I try to find the honest reviews is by ordering by "recent", instead of "popular". That way you're a little more likely to get real reviews, instead of paid.