It doesn’t answer your specific question and isn’t meant to be preachy, just want to say that I’m shocked more people don’t use public libraries for books they don’t want to keep forever. Check it out as often as you want, no need to keep it on a shelf, if you really love it, then buy it.

I just want to let you know that abebooks is owned by Amazon.

Last book I bought online was from Wob. World of Books. I don’t think they are owned by Amazon.

Really surprised nobody has mentioned Better World Books yet. Good selection of books, most of the used books seem to be former library books, and they (at least claim) to donate books to charity with every purchase.

You can get really cool books for really cheap with their bargain bin sales too.

I’ve also tried ThriftBooks but I got too many bad copies - one book, Lord of the Flies, which was owned by a high schooler and had writing on every single page of the book and another book which clearly had urine of some kind on it judging by how obsessed my cat was with the yellow stain on the spine. Their edition picker is also terrible, very similar to the way Amazon handles their options to where different editions are all smashed into one page.

Biblio is a solid but not perfect

AbeBooks. Usually better prices than Amazon, too.

If you want digital books the high seas provide plenty now.

Depending on what kinds of books you’re into: https://www.pmpress.org/ https://www.akpress.org/