Over the top, interesting story... but is it long enough?
Anyway it's a really exciting game but after about the 3rd level i looked down at the amount of levels left and there were only a few left. It was a real bummer that there are only 6 levels. But after beating the game the directors cut is available which has a few more zombies but its all still a little depressing. The good thing is tho that you forget all about what happens next when you play the level again because you're so focused on shooting the zombies and you don't move. If you're up for more of a challenge after beating the directors cut try story mode again dual wield. It's really intense. and click the extra mutants button. It'll seem like a whole new level in the same place. :)
So I'm glad to say that the game has a lot of replaying capability and it's quite perfect if you need something to do with another friend since they can join right in.
As for the difficulty... I pretty much suck at games so it was just right... but once you get the shot gun you just pick off the zombies so it's really easy.
Overall I'd say the game was very fun and exciting with a great story... but I wouldn't buy it for 50 dollars. I'd just rent it and you'll be done with it in about 2-3 hours.
(I hope that all made sense... thanks for reading!)