Books like Magic Kingdom for Sale/Sold

Landover was a genuine magic kingdom, complete with fairy folk and wizardry, just as the advertisement had promised. But after he purchased it for a million dollars, Ben Holiday discovered that there were a few details the ad had failed to mention. Such as the fact that the kingdom was falling into ruin. The barons refused to recognize a king and taxes hadn't been collected for years. The dragon, Strabo, was laying waste to the countryside, while the evil witch, Nightshade, was plotting to destroy no less than everything. And if that weren't enough for a prospective king to deal with, Ben soon learned that the Iron Mark, terrible lord of the demons, challenged all pretenders to the throne of Landover to a duel to the death - a duel no mere mortal could hope to win. But Ben Holiday had one human trait that even magic couldn't overcome. Ben Holiday was stubborn.