Maurice, a talking cat, leads a group of talking mice and a stupid-looking kid into a town called Bad Blintz looking for one last score with their pied piper scam. Only Bad Blintz has troubles of its own...
Terry Pratchett really knows how to write a kids book. I would have devoured this thing when I was a lad. Maurice and the rats are good characters, as is Keith, the aforementioned stupid-looking kid. The origin of Maurice and the rats' intelligence was fairly well done. Hell, it's a fantasy story. How much explanation do you need? Pratchett took the classic story of the pied piper and Discworld-ed it up with questions of philosophy, destiny, and leadership. And rat-kings.
Why only a three? The rat king bit felt tacked on at the last minute, although I enjoy me a good rat-king. While the humor was good, I didn't feel it was as good as the adult Discworld novels, subtle sex jokes excluded. Being a Discworld novel, things didn't quite end up all hunky-dory at the end but it was still a good ending.
Pratchett crafted a good young adult novel here. If you have some YA's in your house, go ahead and nab this one for them.