You can learn more about the book here - http://en.wikipedia.org/wiki/Magic_Kingdom_for_Sale_—_SOLD!
Plot Summary -
The novel begins with Ben Holiday, a trial lawyer from Chicago, lamenting the loss of his wife and unborn child in a car accident. He finds an advertisement in an upscale Christmas catalog claiming to offer a magical kingdom for one million dollars by a man named Mr. Meeks. Although skeptical, Ben pursues the offer out of a desperate need to start a new life. Ben receives a magical medallion and is transported through a swirling mist to the kingdom of Landover. He learns that Landover is a world that connects many other worlds such as Earth. It is surrounded by the Fairy Mist wherein reside creatures of Fairy that created Landover and guard the passages to these worlds. Unfortunately, he finds it not exactly as described. He soon finds that Landover has not had a true king in twenty years. The son of the last king did not wish to take up the throne and escaped with the court wizard, Meeks, to Earth. They have been selling the throne to dozens of people in the past two decades, but no one has been able to face the challenge and successfully complete so much as a few months as king. Further, kings of Landover used to be protected by a magical knight called the Paladin, but he has not been seen since the last king's death.
I've been thinking that this book and the world "landover" would be a perfect fit for a D&D campaign, and it maybe something I might consider down the road. The only thing is that it could be construed as being a bit kid friendly, but that's alright actually. Of course I'd have to re-read the book!
Here is a link to the world of landover (what is cool is there is a list of all the characters! so you can easily start creating NPCs like right now) - http://en.wikipedia.org/wiki/Magic_Kingdom_of_Landover
And here is a map of Landover, it just sorta makes you start thinking doesn't it.