Thinking about writing a book? Thinking about selling the book that you're thinking about writing? Then it's time you started thinking about an ISBN number.
ISBN stands for International Standard Book Number and it is required if you intend to sell your book at a retail store or through a wholesale distributor. If you give away your book to friends, or sell a title to an individual, you may not need one. An ISBN is like a VIN number for a car - it distinguishes YOUR book from all the rest. It is a unique identifier that no other book, in any other format, may have. It is yours and yours alone.
This is beneficial for two main reasons:
1) Searchability - Any wholesaler, retailer or individual will be able to type your unique ISBN into any search engine. As long as the book has been registered with an ISBN, it will be searchable for purchase, or to obtain general information about your book.
2) It avoids confusion - Your title, "The Greatest Book Ever Written" is available for purchase, but searching by book name only may result in 100 or even 1000 books with the identical name. How would a potential buyer know the difference, other than scrolling tediously through countless titles? With a unique identifier (your ISBN), there would be no question that YOUR book belongs with that ISBN.
It is important to note that each different published format of your book (print hardcover or paperback, digital, or audio) will need a separate ISBN. Your publisher can issue an ISBN. For self-published authors, you can purchase one through www.bowker.com, which is the official source of ISBNs in the U.S.
Your book is unique! Assign it an ISBN and it will forever be recognized this way!