We’ve all seen those 10 or 13 digit numbers on books, prefixed with the initialism ISBN. They’re found on the back of paper books, and more often than not, with their respective barcode. When you open the book, the ISBN is also found on the first verso (left hand page).
When you open a digital edition of a book, standard placement of an ISBN is to be on the second page (after the title page). Sometimes they’re there, and sometimes they’re not. If you’ve ever wondered why ISBN’s appear at times, and not at others, then this discussion should answer that mystery…and a few others too.
What does ISBN stand for?
ISBN stands for International Standard Book Number. So, when you hear or read of an ISBN “number,” it’s a bit redundant. As for its history, “ISBN (International Standard Book Number) is an international standard first published under the auspices of ISO (the International Organization for Standardization) in 1972.” 
Up until 2005 there was a 10 digit classification system. As its significance and acceptance grew world wide, there was a need to increase the capacity of the system. A 13 digit classification was approved.
What is an ISBN used for?
An ISBN is a product identifier, which is used by publishers, booksellers, libraries, and internet retailers. It is used to identify one-off publications, which are publications that occur once (a “one-shot” deal, for example). These one-off publications include books, individual sections (such as chapters) of books, issues or articles from journals, a treatise, booklets, maps, educational/instructional films, videos and transparencies, audio (talking) books on cassette/CD/DVD, Braille publications, and so on. However, periodicals such as journals or newspapers are not included within this one-off category. (ISSN [ISO 3297] identify those type of periodicals, for those of you that are interested.)
The ISBN identifies the registrant of the book, in addition to its specific title, edition, and format. Any book that is made publicly available, whether for sale or not, can be identified by ISBN. Being identifiers, ISBN’s help when ordering or listing those one-off items, and helps with inventory control. Some relate the ISBN to the metadata of a book. As the website states: “The ISBN is the global standard for identifying titles.”
Does an ISBN help to protect your printed work?
“The ISBN is an identifier and does not convey any form of legal or copyright protection.” Although ISBN use is mandatory in some countries to identify publications, it isn’t in the United States. If American authors are looking for legal protection of their written intellectual work, look into copyright protection. 
Whether or not to use an ISBN is strictly up to the publisher. Is an ISBN necessary? Not necessarily, but that’s up to the publisher to decide. And when the word “publisher” is used, that can refer to the sole author or a publishing house.
Then why bother with an ISBN? What are the benefits?
Ka-ching! Meaning, there’s a better chance that it’ll increase your sales potential. It maximizes your visibility in the publishing world.
Some book outlets are reluctant to carry books or ebooks unless an ISBN is registered. Take for example a book distributor that plans to carry a specific book. When a book has an identifier, it alleviates their burden of manually cataloging and inputting detailed (meta)data to specify the book’s title, author, publishing house, copyright date, and other details that separate it from similar books.
Before the 1970’s, manually inputting data was the only practical way to catalog books. Nowadays, with ISBN’s, why should any book distributor bother handling a book that doesn’t have a convenient one number system to help them keep inventory? Without an ISBN, the book simply becomes a low priority item. And if a book distributor doesn’t want to carry your books, there’s less exposure to outside readership and less chance that readers will know your book exists. It’s simply a bookkeeping thing.
It’s more efficient for distributors to input an ISBN instead of a whole lot of data. As they say, “A picture is worth a thousand words”; an ISBN is worth, well, perhaps a couple of hundred at least: 978-7-309-12310-4. (A seemingly obscure book store for Americans, yet the ISBN pinpoints to one [of many] of my books regardless of Internet/geographical locations and boundaries.)
- Quick review of why ISBN’s help the author.
- The ISBN is recognized internationally.
- Information on available books can be found easily.
- Ordering and distribution of books is mainly executed by ISBN.
- Many publishing and supply chain systems are based on ISBN.
- An ISBN is required at electronic point-of-sale systems in bookshops.
- When an ISBN is made machine-readable, such as a bar code, it’s fast to scan and avoids mistakes.
Who should apply for ISBN?
The publisher of the book. It can be the publishing house, or an individual. An individual, meaning, the author that has decided to publish their book themselves.
Basic guidelines on using an ISBN
- Most importantly, an ISBN should never be reused.
- ISBN barcodes are only for hard copies, not digital.
- Use the 13 digit ISBN. Do not use the older 10 digit ISBN.
- ISBNs are located on the first verso. Place it onto the back cover of a paper book too.
- The ISBN should always be easily legible, and large enough to be easily read. It’s suggested to use a 9-point font or larger.
- A unique ISBN is required for each different format of an electronic publication.
The last item confuses people.
A unique ISBN is required for each different format of an electronic publication.
There. It’s that simple. Don’t over complicate it, yet many people do.
“Each different format” is just what it means: An EPUB, PDF, and MOBI are all different formats of a book. If you plan to release the same book title but have three different electronic formats (EPUB, PDF, and MOBI, as above), you need three different ISBN’s.
A possible reason for this confusion….
Americans tend to use Bowker to purchase and keep track of their ISBN’s. Why Bowker? Because it’s recommended by the International ISBN Agency. To see why, follow the link and use the “Select an Option” drop-down list to find the United States. The “Organization” listed is R.R. Bowker, LLC – US ISBN Agency. 
If you purchase an ISBN and fill out the on-line forms for your ebook, then under the “Format and Size” tab, the “Medium and Format” for a digital book will simply be “E-Book” and “Electronic book text” respectively.
It appears misleading that a person’s one ISBN covers all electronic formats for that title. It doesn’t work that way.
Here’s an example from the ISBN Users’ Manual International Edition of how the same title could be displayed for sale: 
- ISBN 978-951-45-9693-3 (hardback)
- ISBN 978-951-45-9694-0 (paperback)
- ISBN 978-951-45-9695-7 (PDF)
- ISBN 978-951-45-9696-4 (EPUB without DRM)
- ISBN 978-951-45-9999-5 (EPUB with ACS4 DRM)
ISBN use differs in many countries
Since ISBN’s are internationally used, each registrant must look to their own country’s agency to see how their country’s laws affect ISBN user responsibilities.
ISBN Bar coding https://www.isbn-international.org/content/isbn-bar-coding