http://techcrunch.com/2014/08/21/there- ... e-minutes/
In an interesting post, writer Claude Nougat estimated the total number of books on Amazon – about 3.4 million at last count (a number that could include apps as well) and then figured out how many books were added in a day. Nougat noticed that the number rose by 12 books in an hour, which suggests that one new book is added every five minutes. And, most likely, it’s probably an indie book.