The International Standard Book Number, or ISBN, is the unique, 13-digit identifier used by publishers and libraries to organize and track books made available for sale.
But for those of you interested in self-publishing, take note: it’s far more than just a tool for librarians or distributors.
It is the number by which sales are tracked on each individual published work you have in the marketplace. That’s really important when it comes to selling your ebooks and paper books on Amazon, Kobo and iBookstore, where sales ranking can have a major sway on impulse buyers.
In the United States, authors pay for this service. They can purchase a single ISBN for $125, buy a group of 10 ISBNs for $250, 100 for $575, or 1000 cost $1000.
You don’t need to obtain a separate ISBN to sell your books in another country (after all, that’s the “I” in ISBN). Typically authors obtain the number in their country of residence.
You need to obtain a separate ISBN for a book that has multiple editions in which the content of that book has changed in some measurable way. On the other hand, when it comes to ebook publishing, you can use the same ISBN on a single work that is being formatted in both epub and mobi formats when making your work available on Kobo, iBookstore and Amazon.