I consider myself pretty well-versed in WDW stuff. Even though before my one trip last year I hadn't been there since 1993, I absolutely devoured the Unofficial Guide, Birnbaum's, and this and other message boards, and I pretty much emerged very well-educated.
A few months ago, I clicked on the link that you spoke of. I e-mailed the author and asked for details about the money back guarantee. He very nicely responded by e-mailing me the link to download the book, putting me on my honor that if I found the book useful I would then pay him.
I didn't have a problem with the book, but after looking at the table of contents and checking out a few key sections, I confidently determined that there was nothing new in there for me, that there was no info in there I wasn't already aware of which would save me time or money or bring my family an improved WDW experience.
This is not to say that it's not a good book. It's just that I've picked up so much info that the book just wasn't necessary for me. I wrote back to the author, and he acknowledged that someone who is already very well-informed will get much less out of the book than someone who is newer to the WDW experience.
I'm sure if I'd seen the link and bought the book before I got to the other books and the message boards, I would have been greatly helped by the book and saved money by following its leads.