There are lots of numbers floating around that purport to show how big the e-book industry is. The Association of American Publishers AAP says that ebooks are the single best-selling category in U.S. publishing. Amazon AMZN says that ebooks are its most popular category of book format. A growing number of independent authors, selling ebooks without a publisher, are making significant numbers of sales.

All the numbers suggest that e-books have some serious momentum. But when you look at all the data together, it’s clear that no one knows how big the business is, because the information is woefully incomplete. There’s no way to tell how many e-book titles sell, the most popular genres, or even who the most important publishers are.

via Guess What? No One Knows How Big the E-Book Business Is [Update] | BNET.