Lord of the Flies, by William Golding

Very good book. It's one of Stephen King's favorites (he actually has a character from one of his books reading it), which was the main reason why I picked it up.
As it turned out, it's also about one of my fav plots: what happens when a group of people are left alone, cut out from civilization.
In this case, the group of people are schoolboys, who are being evacuated during a world war (in the future) and are left alone in an island.
At first, they enjoy the sudden freedom, but soon they start a steep descent into savagery, which will only lead to violence and destruction. The author's point of view is that, without the rules of civilization, man becomes beast.
The main character is Ralph, the elected chief of the boys. He is torn between two forces, represented by Piggy and Jack. Piggy is the fat, spectacled and asthmatic "outlaw" in the group of boys, but he is also the voice of reason and civilization. He is always thinking about how to get organized and what to do to get rescued.
On the other hand, Jack represents the savage. The leader of the choir, he is ashamed when he is not elected chief, and turns into the group's hunter (still commanding the choir boys). He becomes obsessed with hunting and killing pigs.
Events are precipitated by a fight between Ralph and Jack over the signal fire, and the break from civilization is enhanced by an irrational fear of "the beast", a fearsome creature that is supposed to live in the island.
The book is full of symbols and allegories that get you thinking about the true nature of men.