The graphics arn't impressive, the storyline is non-existant, but its extreamly fun and addictive for everyone.
It takes a comical approach to something very basic: Zombies are swarming in around you and you have a bunch of great weapons to fight them off. Lawnmower, brain gun, cricket bat, a gun that makes them dance via thriller, among other weapons bring a lot of fun in an addictive (and cheap) package.
Its easy to catch on: zombies are closing in. Take out your torch to make them retreat a bit and allowing you to run through them. Zombies on fire will increase your score multiplier but will come at you faster than before and won't fear the flame anymore. Weapons will pop up and you will use them to blow away hordes and hordes, literally thousands of zombies. The more you kill, the different types of zombies will spawn and make the game very difficult.
It does support co-op, but there are isn't a multiplayer available. There are a few player modes: The default is to kill zombies until they stop comming and allowing you to play to the next stage until there aren't anymore stages. A time mode requires you to collect clocks by torching and killing zombies. Kill enough zombies and you continue to the next stage. Protecting Daisy has you protect your girlfriend parked in a car from zombies that want to eat her brains (and steal your ride?). The last is a special level that has you meet certain requirements to beat the stage: I.E. Trick zombies into running into electricity in order to die. Using an explosive brain to blow up nearby zombies in order to kill them instead of using your gun etc.
Easy to play, hard to master, highly addictive and just a blast to let loose and have fun with.