Many successful indie authors do not use ISBNs (for their e-books), and they see no reason why they should. The number Amazon provides works just fine from a practical standpoint.
Having said that, an ISBN gives your book added credibility and has more universal recognition than an ASIN (Amazon Standard Identification Number) when searching for a book by number. So I opt for an ISBN.
However, buying an ISBN costs money. In the United States, buy ISBNs from Bowker. Currently, the standard price for one ISBN is $125, ten costs $295, and one hundred costs $575.
Note that you will need one ISBN for each format your book is in: Hardcover, paperback, e-book, and audio, so that’s four ISBNs. Given the costs, I see why many indie-published authors skip them.
Peter Lyle DeHaan, PhD, is an author, blogger, and publisher with over 30 years of writing and publishing experience. Check out his book The Successful Author for insider tips and insights.