The guides are filled with all kinds of interesting facts about how the rides and parks turned out the way they did, and most importantly why.
For example, in the Magic Kingdom edition they talk about the design and construction of Cinderella's Castle and why it ended up at the exact height that it did. It's 198 feet tall. The reason Disney chose that height is because any building in Florida that's 200 feet or taller is required to have a blinking red aircraft warning light on top of it. Obviously Disney didn't want a blinking red aircraft light on top of their centerpiece castle, so they made it as high as they could (with a little room to spare) so that they could keep their design and not have to spoil it with a red blinking light. The same consideration went into Spaceship Earth, Tower of Terror, Space Mountain, and the other tall ride structures in the parks.
If you're a Disney fanatic and finding out those types of little facts is interesting to you, then these are the books for you! I've had more than a few good laughs and "Aha!" moments while reading them. Things that I always wondered about since I was a kid are explained here for the first time.
The books also show a lot of interesting photos and sketches about how the parks and rides were originally conceived versus how they turned out. In some cases they're almost exactly the same, and in others there were key design changes made along the way. Those design changes are explained as well. Interesting stuff....
These guides are inexpensive and well worth the money to get some more insight into the terrific Disney design principles. If you decide to purchase them, watch out! They're going to make you want to go to The World to check the parks out all over again! :-)