I'm not sure how sustainable they are, but there are a couple of used bookstores near me. I think they engage in heavy curation, though -- they'll pay for your

I'm not sure how sustainable they are, but there are a couple of used bookstores near me. I think they engage in heavy curation, though -- they'll pay for your books (or even do consignment for rare/expensive ones), but only if they think they're likely to sell.