World War Z, by Max Brooks -- simply amazing.
The main idea is the question of what would happen if an epidemic of zombieism (is that a word??) started to take over the world. One bite by a zombie and when you die (for whatever reason) you come back to life as a zombie.
Brooks' zombies want to eat human flesh. They have no intelligence and cannot run. They also can't be scared, nor can they be stopped by anything other than a direct head wound.
They are also taking over the world -- eating/infecting as many humans as they can.
The brilliant aspect of the book is that it is centered around interviews given after the Zombie war was won. Each interview is self-contained and tells part of the story of the way the problem originated in China, was spread worldwide and finally how the war was won.
It is about 7 hours long -- get it for your next trip or put it on your ipod for your commute. It will chang the way you look at t he world.