The prices we pay are based on the current demand we have for each particular title. All books we buy must be in good condition. The bindings must be in good shape, with covers and all pages intact. The pages must be readable. We want to buy current edition books that your professors have ordered for use next term.
Publishers issue new editions of textbooks frequently.
They do this partly as a result of changing information, but also to discourage the sale of used books. When a new edition of a title comes out, the previous edition loses its value. Old edition textbooks are in surplus in the national used book market, and there is no demand for them. You may wish to keep these books for your own library since they can still serve as valuable references. If your text was sold as part of a package containing both the book and a computer disc, an audio tape, or a workbook, these items must be included when you sell back the book.