Here's something I've seen done -- even by the big companies -- in the way of free promotion to get a product "out there."
They will put their software, music, BOOKS, on the file-sharing networks -- KaZaa, BearShare, LimeWire -- USING KEYWORDS -- with full knowledge that people will freely download their product, but they also know their product will get exposure. To an audience, at any given time, of 3,700,000 KaZaa users (does not include BearShare or LimeWire).
You could technically put a portion of your book on the file sharing networks, and instruct people to contact you about the full version.
If I want to promote anything reasonable and hit tens of thousands, worldwide, I use IP messaging software. You can find this at www.offers.wonderpopup.com. It works.
Extreme Web Design and Internet Marketing