I remember getting some questionable quality books from amazon which didn't match up to the usual standard of a publisher. No Starch Press called this out in the past saying amazon sell counterfieght books. https://x.com/nostarch/status/1183095004258099202

I'm not sure what actually happens, but I mostly stopped buying paperbacks on Amazon a good while ago, and if I do, and I'm unhappy with the quality I'll return it.