The Verge says:

According to a new report by Bowker, which provides ISBNs for books in the United States, self-publishing has increased by 287 percent in the last five years, accounting for 43 percent of all print books in 2011. Printed versions accounted for almost two-thirds of self-published titles as of last year, but ebooks are on the rise: Bawker notes that self-published ebooks grew by 129 percent from 2006 to 2011, while traditional print books increased by 33 percent in the same period.

I've said this many times before: 99.9 percent of all self-published books are not ready to be published. They haven't gone through the editing (or, for that matter, copy editing) process. A book isn't a book until it's been edited. (Not "beta-read" by a very stern friend or relative—edited, by a trained editor.) And it always happens that after I say 99.9 percent of all self-published books are not ready to be published, I get a deluge of self-published books in the mail from self-published authors who claim to be part of that prestigious .1 percent of authors, because their books magically don't need editing. Trust me: Your book needs to be edited. You're not in the .1 percent. Just because it's a bunch of words shaped like a book doesn't mean it's a book.