eBay, you can also try bigwords.com which checks multiple buyback sites for the highest selling price. Source: 12 months ago

When I was in school, I used bigwords.com to buy any physical copy of a textbook I needed. It's a comparison shopper, and checks the difference between buying and renting at several stores. Source: over 1 year ago

Echoing that you'll probably get very little or no money from them, but my recommendation is to try bigwords.com. You can load all of your books into your cart, click 'sell' instead of buy, and they'll aggregate the best websites to buy them back (considering combined shipping, etc). Source: almost 2 years ago

Amazon has a lot of good used book listings, there's also bigwords.com to find used books (since you mentioned you don't like reading books on screens ...which is also awesome!). Source: almost 2 years ago

It seems like, you might have more luck with books than with trying to piece things together from bits and pieces on websites - I possibly don't know any books about Sumerian mythology, sorry, but searching your local library or alibris.com (because Amazon are crooks) might get you something that'll give you a general idea of what archaeologists know about Sumer and its mythology, and give you somewhere to start... Source: about 1 year ago

I buy used books at alibris.com, but, apparently, they work with sellers (20 USD per annum). I takes an investigation to check out those. Source: about 1 year ago

Highly recommend checking out alibris.com as well. Source: about 1 year ago

I collect first edition / first printings of rare science fiction from the 60s/70s/80s. I've found abebooks.com and alibris.com to both be excellent when trying to find obscure pieces. Source: about 1 year ago

Drive-by comment to recommend http://alibris.com as a great used book, music, dvd source. Source: about 1 year ago