More than four years ago we invested in Dan Poynter's books especially his self-publishing manuals and I mostly have read those and Tim some. In it he gives formatting advice among other things. He might have self- published anywhere between 80-200 books if not more. He sells a lot of epubs on his site as well at Parapublishing.com In those publishing manuals he highly recommends getting bar codes and ISBNs with the company Bowker. Bowker has great deals which include using Vook distribution to spread your ebook to Amazon, iBooks, Barnes and Noble, Google, Kobo, and Blio etc.