People have perfectly good, popular books that they don't want anymore. The library has holds on these popular books because there aren't enough to go around. Could a section of the library hold donated books for people to take? Maybe show your library card so it doesn't turn into a free-for-all for used book sellers. Instead of all the books going to the library book sales, they could go to a neighbor exchange. Or if the library doesn't want to handle it for paperwork & bureaucratic reasons, do it at the rec center.