on Indie Kids Books:
Do you remember Y2K? When the century turned from 1900 to 2000, computer programs were in trouble. For many programs, the date had been programmed as 19__ and there was no easy way to re-program it to 20__ or just ____. The book industry is having its own version of a computer programming meltdown.
ISBN – International Standard Book Number
The ISBN is a unique identifying number assigned to a book title/format. That is, each format—hardcover, picture book, ebook, audiobook—needs its own identifying number. The number is tied to both the title and format.
About fifteen years ago, the 10-digit numbers that had been used since the inception of ISBNs was becoming too full. To alleviate this, the industry converted to 13-digit numbers, starting with 978. But they warned that when that series of numbers was used up, they’d move on to 979 and other series.