As another resource document explains, every book published in the United States since 1970 carries an ISBN. An ISBN is a series of numbers usually appearing on the back cover. Books published before that decade may have Standard Book Numbers, or, unfortunately, they may have no identifying numerals at all.

Don’t worry: you may still be able to sell your used books using BookScouter. The website features a handy search tool. Enter information about the book–its title, author, and date of publication–in the form provided. We can try to locate the ISBN for you.

Alas, if your book really doesn’t have an ISBN, we can’t help you sell it on BookScouter . Our vendors require each of the books they buy to have one. There are many dealers who buy and sell rare books, collectible books, and first edition books. They include AbeBooks, Peter Harrington Books, and Bauman Rare Books, among others.

So, sell your rare or antique book to an appropriate dealer, but continue to bring to BookScouter your used textbooks and other works you won’t read again.