I used slugbooks in uni to great success. Stupid freshman me bought every suggested book without second guessing. I got the hard cover and the binder variant (which doesn't come with a binder) of my chemistry textbook. After that I was a lot more careful.
Hmmmm. I tried Fulgrim (book 5 Horus heresy) and got prices WAYYYYYY higher than what I paid on eBay like two weeks ago. So………..
Another similar site is booko, which started in Australia 10+ years ago.