Ideas for Selling New/Used Books?

I have a bunch of books in my apartment that I’ve read, and I just don’t have the space to keep them all like I’d like. I know of a few places in NYC that allow you to sell them books, but wanted to see if there might be a better online option.

Anyone know of any good sites that buy used books? I’d rather not have to individually list on eBay or something like that - rather I’d like something where I can possibly just send a whole box at once to an organization.