in Publishing
Four ISBNs for one novel
Hardback, paperback, ebook and audiobook are four products to the book trade, and each needs its own number.
Dreamscape Code has four ISBNs: one for the hardback, one for the paperback, one for the ebook and one for the audiobook. To a reader they are one book. To the book trade they are four products, with four prices, four formats and four sets of stock, and an ISBN identifies exactly one of them.
The numbers
Hardback 978-1-0654431-5-5. Paperback 978-1-0654431-0-0. Ebook 978-1-0654431-1-7. Audiobook 978-1-0654431-4-8. All four come from the Tingle Press block, which is why they share the same prefix. The print numbers are printed as EAN-13 barcodes on the back covers and appear on the copyright page; ebooks and audiobooks carry no barcode.
One ebook number, many stores
The same EPUB file goes to Kobo, Apple Books, Google Play and Barnes & Noble, so they share the single ebook ISBN. Kindle is the exception: Amazon does not need an ISBN for a Kindle edition and assigns its own identifier, the ASIN, to the same file.
Why owning the numbers matters
Some print platforms offer free ISBNs. They work, but they usually name the platform as the publisher of record and can only be used with that platform. Using the press's own numbers identifies Tingle Press as the publisher of every edition, so the book can be printed, distributed and listed wherever it needs to be without changing its identity.
The rule of thumb is simple. If a reader could buy it separately, it needs its own ISBN.