How many ISBN numbers do I need?
If you are self-publishing a book, you will need one International Standard Book Number (ISBN) for each format of your book (e.g. one for the print version, one for the epub, etc.).
The ISBN is a unique identifying number that is assigned to each book and is used to track and catalog published works.
In most countries, ISBNs are managed by a national ISBN agency, and you will need to purchase ISBNs from the agency in your country. In the United States, the ISBN agency is Bowker, and you can purchase ISBNs from them directly or through an authorized reseller. The following link provides more information about where to get an ISBN: https://help.ebooklaunch.com/article/39-where-to-obtain-an-isbn
It's important to note that ISBNs are not necessarily required for self-publishing. Still, they are recommended as they make it easier for bookstores, libraries, and online retailers to catalog and sell your book.