Think of your book, or "title," as it's called in the industry, as your child. Think of each format as your title's child, each with that title's DNA.
Each title needs an ISBN, or identifier, for each format: paperback, hardcover, ebook, audiobook. If it helps, think of ISBNs as birth certificates for your grandchildren.
When you take into consideration other formats, like Spanish language and large print, you realize that you're growing quite a large family.
What's wrong with free ISBNs?
Here's what happens with the freebies. Your paperback at Amazon is marked with Amazon's DNA. The DNA for the IngramSpark paperback looks exactly the same but is marked with their DNA. So now you've got identical twins, but they're not really yours. They're clones.
Now, what if you want to try out Draft2Digital's POD service, or StreetLib or another service, and you use their free ISBNs?
Dang! You've got quintuplets!
Think of it like this. You can call and see how they're doing, but you're never in the same room. It's like they're on permanent sleepover at a friend's house, and you have to get the friends' parents to report on their progress and update their metadata.
Okay, maybe I have gone a little too far with this analogy but I hope you're getting the drift.
The upshot is, to do business as a professional author-publisher, you need your own publishing imprint and ISBNs so you can mark your books with your DNA. It's all a part of becoming a professional author-publisher.
Get IBPA's Industry Standards Checklist for a Professionally Published Book free on their site and make sure your book has all the right elements and looks like any book published by one of the Big 5 publishing houses.
Experts agree that ISBNs, along with editing and design, are the three items you need to pay for. Professionalism counts!
Learn more about ISBNs
I've addressed this question in even more depth in a post on the Self-Pub Boot Camp website, with a link to a free webinar, too. You'll learn more about ISBNs, what the numbers mean, why you need your own, how much they cost, where to get them, and how to apply them. Go to this post to find out why it's essential for authors to own your own ISBNs.
