IMO most people get into AM because they're the 'workng poor' to begin with. Then you buy products that promise the world and don't so you become leary of it all. I would maybe offer a free download of a chapter or table of contents, and/or a money back guarantee. Maybe a private blog with access for members only? Just thinking out loud.
As a librarian I can say we have a love/hate relationship with Google. There are some really old books that are available full text. I wrote about it at Squidoo.