Used quilt books are hard to come by in my part of the world. There are two places I give my books to when I am willing to give them up. My University library has a "Friends of the Library" group that sells donated books to generate money for the library. The Symphony Book Fair in town accepts book donations, too. Perhaps you have those kinds of book sale events to support public nonprofits? If you go to guild meetings, that would be a great place to recycle your quilt books. It's a shame you don't have a Half Price bookstore in your town. They are all over Texas and I bet they would be drooling to get access to a bunch of quilt books. They only buy in person, unfortunately.