Yesterday, I discussed why it really is important how you acquire an ISBN for your book and who actually owns that number. Now, let’s consider what those 13 digits in an ISBN mean to the book industry (publishers, wholesalers, distributors, and retailers).
I suppose I should first note that there are, in reality, two versions of ISBNs you will encounter — the ISBN-10 and the ISBN-13. What’s the difference? A few years ago, the ISBN folks realized that they would soon exhaust the mathematical possibilities of the 10-digit format. Too many books were being published in too many different formats. The solution was obvious — expand the format to incorporated more digits. You might think that adding three more digits would increase the available numbers by a factor of 1,000…but you’d be wrong.
It only doubled them.
How could that be? you might wonder.
First, if you’ve ever looked at the bar code on the back cover of a book, you might have noticed that the ISBN is usually printed in human-readable (i.e., in numerals) just above the bar code. Up until recently, that was the 10-digit ISBN. Then, during a transition period, it frequently included both the 10- and 13-digit forms of the ISBN. Now, most newly published books will show only the ISBN-13 (although some are still including both). You might also have noticed that there are human-readable numerals sort of embedded along the lower edge of the bar code. Those digits are the ISBN-13…and always were (even when there was no such thing as an ISBN-13).
In the days of only ISBN-13, the bar code and the embedded numerals (technically known as the Bookland EAN, or European Article Number) consisted of the ISBN-10 plus a 978 prefix and, usually, a different final digit.
Today, the EAN and the ISBN-13 will be identical.
Confused yet? Hold on. Let’s decode an ISBN-13 to, I hope, clear things up.
The ISBN-13/EAN consists of five distinct parts:
- 978 or 979 prefix (all this means is that the number refers to a book — after all, the EAN is used for a lot of other non-book products with their own unique prefixes)
- Group or country identifier (for books published in the English group — meaning the US, UK, Canada, Australia, New Zealand, etc. — this will a ‘0′ or a ‘1′)
- Publisher prefix (this can from two to seven digits, depending on the size of the specific block of ISBNs)
- Title identifier (this is actually the part that is assigned to a specific title, edition, and format published by the publisher identified by the publisher prefix)
- Check digit (the last digit in the ISBN, always just a single digit, that is calculated using a specific mathematical algorithm and only really matters to computer databases and such)
Note: To date, nobody has been assigned an ISBN block with the 979 prefix, but R. R. Bowker expects to begin issuing those later this year.
Real-World Example: 978-1-934631-21-8
Right away, you can see the 978 prefix that tells us this is a book. The next digit, the ‘1′ following the first hyphen, says it was published in one of the English group countries. The next set of digits (934631) is the publisher prefix. If you looked up this prefix in one of the industry databases, like Books-in-Print, you would find out that 934631 identifies Slipdown Mountain Publications LLC…and only Slipdown Mountain Publications LLC (that’s the company for which I serve as the publisher). Nobody else will ever be issued that specific publisher prefix.
The next set of digits (21) represent one specific title, edition, and format in the block of 934631 publisher-prefix ISBNs. In this case, it is the first edition of my own book Devil in the North Woods and, specifically, the e-book format of that book. No other book will ever use the title identifier 21 with the publisher prefix of 934631 and the group identifier 0. And that’s what makes it unique. And what makes sure nobody orders an e-book format for this book when they really wanted the paperback format.
Note: The paperback format of that same book has a different ISBN (in this case 978-0-9746553-1-4, which also has a different publisher prefix since our company owns two different blocks of ISBNs although both point only to us).
And then there’s the final, check, digit (8, in this case).
By knowing the publisher prefix, you can immediately determine the size of that block of ISBNs. Since there are only 13 digits total, and the 978 (or 979 eventually) plus the group identifier always total four digits and the check digit is always a single digit, there are only eight digits left to work with. In this example, the publisher prefix is six digits, leaving only two digits to assign to specific books and, thus, only 100 possibilities (00-99). Therefore, this represents a block of 100 ISBNs.
Since self-publishers usually buy a block of 10 ISBNs and small publishers typically buy a block 100, anyone who cares can quickly determine the size of your publishing venture.
So, why not just delete the dashes and leave ‘em guessing.
Fair question, but it won’t work. More on that tomorrow.
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