First off, what are ISBNs?
ISBN stands for International Standard Book Number and is a 13 digit long number that identifies your book. Each format of your book (eBook, hardcover, paperback) will have a unique ISBN as well as each language you have it translated to.
If you intend to release multiple books in different formats you can see how the number of ISBNs needed will add up fast.
Should you buy your own?
It depends on where and how widely you want to distribute your book. For example, Amazon doesn’t require an ISBN to publish an eBook through them, so if that’s the only way you intend to release your book then it may not be worth the investment. Amazon will also supply you with a free ISBN for paperbacks.
So why buy your own?
If you choose to use free ISBNs you don’t own them, they are owned by the company that set it up for you. So in this case, Amazon owns the ISBN and you can’t use it yourself. Should you choose to publish or print your book through another company you’ll need a different ISBN. Also, when you use a free ISBN you are not associated with the ISBN as the publisher even though you are self-publishing your title.
If you want to associate your ISBNs with your own Business Entity (for example if you want to set up your own publishing company), I’d suggest setting that up first.
Where do you buy them?
You should purchase ISBNs directly from Bowker. Be prepared, they aren’t cheap. I opted to buy 100 ISBNs because it was more cost effective and I want to get my book out there in as many ways possible. With even one novel it’s easy to see how you could quickly burn through 10 different ISBNs.
Barcodes
Your ISBN is used in the barcode that is printed on the back of your book. Bowker will try to up-sell you a barcode. Don’t buy them unless you intend to print your book through a smaller printing service that doesn’t provide a barcode for you. The big POD (print on demand) services like Amazon, IngramSpark and Barnes & Noble provide the barcode for you, so in those cases it’s an unnecessary expense.
Changes to your Manuscript
As long as you aren’t making significant changes to your manuscript you do not need to change your ISBN. If you add paragraphs or chapters, that’s technically a new edition and would require a new ISBN.
Changes to your Cover
An updated cover does not require a new ISBN as long as the content is the same.
Read Next: Self-Publishing: Setting up an ISBN