A little background on me first ....
Before my first trip with kids in 2005, I did exhaustive research and learned everything I needed to know. It took months, but I loved it.
I kept going to the various message boards every day, and 18 months later in 2006 we were about to go back to WDW again. I saw the ad for the e-book and was curious. I wrote an e-mail, asking details about the money back guarantee. The author's brother promptly wrote back to me. He was very nice, and offered to send me the link to the book for free, as long as I promised to pay for it if I found it helpful.
I took him up on his kind offer. I scanned the table of contents and decided to look at the subject of Disney's Magical Express. All humility aside, except for people whose work involves it, I know as much about the tiny little details of the ins-and-outs of DME as anyone around. Well, their write-up of DME was just plain wrong wrong wrong. So wrong, in fact, that if readers followed their advice it would have cost the readers MORE money (the book incorrectly said that if you are not flying a "participating airline" then you can't use DME and must pay for your own transportation to and from the airport). They had many important details about DME wrong.
I very quickly scanned some other sections. I saw nothing that would save me money that I didn't already know (stay at a Value resort, go during value season, rent DVC points, get a grocery delivery, etc.) since I'd done such exhaustive research and had been to WDW 4 times (but only once in the previous 10 years).
So I wrote back to the author's brother, informing him of the glaring errors I'd found, as well as the fact that I saw nothing in the book that would save me money that I didn't already know.
He was very gracious when he wrote back, and agreed I should not pay for it. He also agreed that the book would be more useful for WDW novices than for very experienced or already-knowledgable WDW guests. So in other words, there are no "insider secrets" ... that is, there are no secrets at all, nothing that you and I can't already know through other means.
I checked back about a week later and they had, in fact, made the appropriate corrections to the DME section.
I think I could recommend the book for people who don't know a lot about WDW and don't have the time or inclination to do their own exhaustive research. It does lay it all out in one place, as opposed to having to hunt for the information in various websites.