Every book needs an ISBN (International standard book numbering), which can also be used to create the barcode on the back of the book. The ISBN is an international number used for books, the idea being that you can always find a book using that number, whereas previously you could not. Different formats of the same book should also have a different ISBN, for example for their audiobook edition, ebook edition and printed book edition.
ISBNs have been highly successful, because if you have an ISBN number you can always find the publisher of a book as well as find where to order the book from. The ISBN makes books available to libraries and book shops. The ISBN information is listed with a book data company such as Nielsen’s, meaning books can be ordered straight from the publisher.
However, in practice, most libraries and bookshops don’t purchase books directly from the publisher, even though that service is usually available to them. What they normally do is go to a book distributor and order the books from them instead. But unfortunately, distributors do not stock all books published, they only stock a selection.
This can create problems. If a book distributor doesn’t stock the book someone is attempting to purchase then some bookshops will say they can’t source the book for a customer, even though they can, but are actually just choosing to only sell books they can get from their particular distributor.
If your book has an ISBN and is registered with a book data company as available, then it is possible for anyone to use this number to source your book.