The ISBN number ties into a catalog of all (registered) books in print. This catalog lists the publisher, access and purchasing information, and descriptive data about each book. For that reason, the publisher needs to apply for the ISBN number. For ordering single ISBN number (1 for $125) or multiple ISBN numbers (10 for $250) or to get more information about ISBN numbers, click here to go to the web site for the U.S. ISBN Agency, Bowker. When you apply for an ISBN number, you can also request a corresponding Bar Code for an additional $25.00. You can put the price of your book in the bar code or you can omit it, whichever you prefer. Unless you are confident in your knowledge of the market, we generally recommend that you omit the price. Then you can change it -- up or down -- depending upon your experience selling your book. You can also request a Bar Code separate from your ISBN Number Application. Click here to request a Bar Code.