Understanding ISBN Numbers

How do I go about getting an ISBN for my book? Does that come after I find a publisher or do I have get it myself?

First let's define what an ISBN is—and we're going straight to the source, Bowker, the U.S. ISBN Agency, for ISBN assignment and registration:

They say:
The International Standard Book Number (ISBN) is a 13-digit number that uniquely identifies books and book-like products, such as audiobooks. (It is not the barcode on the book, but is used when creating the barcode.)

The purpose of the ISBN is to establish and identify one title or edition of a title from one specific publisher and is unique to that edition, allowing for more efficient marketing of products by booksellers, libraries, universities, wholesalers and distributors.

A typical ISBN number has 13 digits and represents five unique entities. For example, the ISBN # 978-12-34567-89-0 is broken down to represent the following:

• 978 is the prefix
  
  
• 12 identifies a geographic grouping
  
  
• 34567 identifies a specific publisher
  
  
• 89 identifies a specific title or edition (each edition—hardback, paperback, ebook, audio, etc—needs it's own ISBN #)
  
  
• 0 is a check digit that is created mathematically to validate the ISBN #

Your publisher will provide the ISBN number for your book.

If you're self-publishing, you will need to get your own ISBN. Some printers provide them (like CreateSpace and others). They generally sell them at discounted pricing, however, your number will usually link your book to them as the publisher of record. If you're only publishing a handful of titles, this is the way to go.

If you're going to set up your own publishing company and are fairly confident you'll be publishing 10 or more titles yourself, then you can register your company with Bowker, the US ISBN Agency and get ISBN numbers straight from them. They are pricey. Single ISBN #s cost $125 each. The price drops significantly if you buy them in batches of 10 or more.