Every book for sale needs a specific reference number called an ISBN (International Standard Book Number). While theoretically any book can be researched by this number, I have found that this is not always the case. Some eBook authors do not use ISBN numbers. This limits distribution, as some retailers (Apple, Sony) will not display them without one. And in some cases, even when a book has an ISBN assigned number, it may not be properly registered or recorded. It is best to try to locate a book by author or title or publisher.
And there may not be just one ISBN for that book. An eBook may have several, one for each format. Smashwords, for instance, does not require an ISBN to publish, but recommends it. It is then assigned to their particular format. You may provide your own if it is a unique number (but just try verifying that – it is more difficult than verifying that a book title has not already been used), you may let Smashwords assign a free one for you, or you may purchase your own. But Smashwords provides a number just for ePub format, no other. If you wish to print that book, for instance, you will need a different ISBN number.
Complicated? But wait. There are different length ISBN numbers. There are nine, ten, and thirteen digit numbers. All books printed (ePub or print) after 2007 will have 13 digit ISBNs. But if you are searching for an older book, you may be looking for a smaller number. If you search by ISBN, your search engine may need to know the difference. Theoretically (again) all books with ISBN numbers are registered with R.R.Bowker, LLC . But if you do not find it there, that does not mean it doesn’t exist. ISBN numbers can be lost somewhere in the machinery.
But as clumsy and sporadic as this system may be, it does at least offer a way to catalogue books from every nation around the world. And with hundreds of thousands of new authors entering the market through electronic publishing, the system is sorely needed.