The game mechanics are fairly simple and easy to learn once you run through it once. It is not even a third as complex as Dungeons and Dragons, and about half as complex as a game of Magic. The rule book is only 3 pages long. To me, this makes the game all the more fun.
You start out with a single piece of the city map. With each turn the players add a new piece of the map(which vary each time) Every time a tile is set down, you add a certain amount of zombies.
Then, like a normal board game, you have cool little mini-figures and roll dice to move. If you pass a zombie, you have to fight it by rolling the dice again. 1 to 3 the zombie wins, 4 to 6 you win. You get threes lives ad three bullets. You can exchange the life for another roll or use bullets to boost your score. Simple and fun.
Where the real competition comes in and when it gets really fun is when you play cards. Cards either boost your status or screw over other players. This is NOT a co-op game. So don't play with sore losers. ;)
The core pack, which I got, includes: 25 map tiles, 50 cards, 6 players, 100 zombies, and life and bullet pieces. A great value for under 20 bucks.
To top it off, there several expansion sets with all kinds of awesome themes. I have my eye on the zombie circus set next!
If you need more info, you can view the rule book online right here