Bowker Identifier Services
Every book requires an International Standard Book Number (ISBN). In the U.S., the ISBNs are purchased from Bowker Identifier Services. As the U.S. ISBN Agency, Bowker is the ONLY official source of ISBNs in the United States.
What shoudl be noted for all first-time self-publishers is that every version of your book: eBook, softcover, and hardcover needs its own ISBN. Furthermore, if you update the book, essentially creating a new version of the book, it requires a new ISBN. Conveniently, you can purchase groups of ISBNs from Bowker.
Originally, I thought I had a solid choice between Amazon-CreateSpace and Lightening Source. But, I’ve come to realize that for first-time, self-publishers, there really isn’t a choice. While Lightening Source, via Ingram Spark, represents an opportunity to publish on an international scale, across e-books and paper copies, the predominate opinion in the industry is that the retail stores and major outlets will not purchase an indie paperback. They want to contract with a company, a traditional publisher. Amazon’s pricing model is also at odds with traditional publishing prices, which creates friction between the two approaches to the industry. (Follow the Hachette-Amazon court suit.)
So, as a self-publisher, trying to get noticed, your best bet is to stay with the “big dog,” Amazon. You can add your paperback versions through Amazon’s print-on-demand (POD) company, CreateSpace.
I believe that your pathway should be to start with Amazon and get noticed. Once your marketing has built your customer base sufficiently, you might receive offers from a publishing house, who can distribute your book through the major retailers. It will take time—marketing and patience.