Here’s the bottom line: If you don’t purchase your own ISBN under your own publishing company name, then you are not the publisher. If you use a publishing services company and let them assign your book an ISBN, they are the publisher, not you. Let’s backtrack a bit and talk about just what an ISBN is. An ISBN (which stands for International Standard Book Number) is to a book what your Social Security number is to you. An ISBN is your ID in the book world. This thirteen-digit numeral unmistakably identifies the title, edition, binding, and publisher of a given work.