There’s plenty of information about listing and selling regular ISBN-13 books. However, what about the books that don’t have an ISBN? How do you deal with them? For one thing, such old books may not have any value; for another, some out-of-print books can be rare collectibles you can sell quite profitably. Therefore, knowing how to find and evaluate as well as where to sell books from the pre-ISBN era is an advantage you can use as a bookseller.