Awhile ago I picked up a pile of books that the library had discarded and put on sale. Libraries frequently weed their collections, getting rid of items that are worn out, old, out of date, rarely checked out, etc. All kinds of great things can be found: records, CDs, graphic novels, classics, biographies, magazines, puzzles, kids’ books, and much more! I highly recommend giving your local library a ring-a-ding-ding to see if they have used items for sale. For even bigger finds you may want to check the main library branch too, as they often have larger collections.
Or heck, if you are planning a trip why not find out if a library along the way has a store, you never want you’ll find. Check out this link to find public libraries.