In August 2011 librarians and information scientists Jana Bradley, Bruce Fulton, Marlene Helm, and Katherine A. Pittner of the University of Arizona, Tucson, published "Non-traditional book publishing," firstmonday.org, Vol. 16, No.8.
"Non–traditional book publishing, prospering on the Internet, now accounts for over eight times the output of traditional publishing. Non–traditional publishing includes books published by their authors and books representing the reuse of content, most of it not covered by copyright. The result is an heterogeneous, hyper–abundant contemporary book environment where the traditional mixes with the non–traditional and finding books that match a reader’s taste is more difficult than previously and may involve new methods of discovery."
The Bowker (2011a) annual statistics on book publishing for 2010, compiled from its Books in Print database, revealed startling news. The output of non–traditional titles was eight times as great as the number of mainstream published books. Traditional new titles are projected to number 316,480, a five percent increase over 2009, but nowhere near the 2,776,260 non–traditional titles reported by Bowker. These non–traditional books “are largely on–demand titles produced by reprint houses specializing in public domain works and by presses catering to self–publishers and “micro–niche’ publications”
"Bowker’s numbers, as startling as they are, do not cover the whole of the non–traditional book output. For the most part, Bowker counts books with International Standard Book Numbers (ISBN)  so non–traditional titles without ISBNs would not be included. Authors who self–publish using their own imprint may not be counted as non–traditional by Bowker. Additionally, the Bowker numbers do not take into account the flood of titles self–published for the Kindle Store through Kindle Direct Publishing (KDL). Non–traditional publishing, therefore, could easily represent a much larger number than the 2,776,260 reported by Bowker.
"Non–traditional titles, according to Bowker in this same report, are marketed primarily on the Web. Another report by Bowker (2011b) shows that online retailers together are the single largest book–buying channel, making access to non–traditionally published books possible for a very large buying public. Non–traditional books, then, form a huge segment of books available in today’s book marketplace."