There's an informative update on self-publishing and digital books here: The Joys and Hazards of Self-Publishing on the Web:
In particular, note:
The single toughest part of self-publishing is getting attention for
your book. Nearly 350,000 new print titles were published in 2011, and
150,000 to 200,000 of them were produced by self-publishing companies,
said Kelly Gallagher, vice president of Bowker Market Research, which
conducts an annual survey of new books.
Same stuff I've been telling people for five years now.