Brad Pitt's a UN investigator, with an odd assignment: He's charged with tracking down the source of a zombie outbreak, in hopes this will lead to vaccine for it before the walking dead overrun humanity's hastily erected defences.
Unlike the normal 'zombie survival' stories - where the scope of the plot is simply 'survive the night', 'get out of the mansion', or 'master the playstation controls well enough to pull off a head shot' - World War Z actually looks semi-seriously at the global reaction to an outbreak of zombies. The failiure of beauracracy to accept what is happening makes the rapid spread of shambling rotters fairly convincing. Better still: The zombies are convincingly un-dead and scary. They're fast, and have some instinctive, but effective, swarm strategies to overrun humanity.
Pitt's just playing the generic action hero, and the big discovery that finally turns the tide doesn't really make sense. Added to this, the film's big strength is also its big weakness: The way it plays the zombie outbreak as a straight up bio-disaster. In parts it makes the zombies much more effective, and in parts it all comes across as kind of ridiculous.
Zombies are always ugly:
"Brains, brains, bra- A date? What's wrong with you!?"
The Verdict: Worth catching - the movie, not zombie-it is.