Harry Potter and the Prisoner of Azkaban
Seriously, how cool is the Marauder's Map? It's pretty darn cool. First off, what does Marauder mean, though? That's a good SAT word to know. "Marauder" means a looter, an outlaw who roams about pillaging and plundering. So, like a pirate, basically. The Marauders themselves – Sirius, Peter, James, and Remus – weren't stealing stuff from Hogwarts (we assume). So what were they "looting"? Well, they essentially looted knowledge itself. They uncovered secrets and found out and did things that students normally don't do. The map itself basically represents the old adage that "a little knowledge can be a dangerous thing." It's fitting that Harry recalls Mr. Weasley's word of caution after he gets the map:
Never trust anything that can think for itself, if you can't see where it keeps its brain. (10.3.52)
The map may be fun and ridiculously awesome, but it's dangerous too. It leads Harry to both truth (namely about his father's past at Hogwarts) and to a lot of danger (such as near-suspension by Snape after his map-sponsored misadventure in Hogsmeade). At least Draco got some much-deserved mud in the face after that.