Genius
The campaign is actually comprised of four smaller campaigns and they are enjoyable. I don't think the shortness of them takes away from the game just because you can beat them over and over again yet still have fun. I personally don't recommend playing this game with an experienced on your first run through. It WILL take away from the game. Of course sadly, that is how I started playing. You aren't supposed to "run through" the missions. You're supposed to take your time and wonder what is around the next corner. This is known from the creation of the Witch. You can hear her cries from a distance and you are always on the lookout for her. That's how I feel anyways. If you sit down alone and play with AI characters, the missions will be at your own pace providing a funner (I don't care that it's not a word) first time play through. The first time I played it, my buddy ran through it and it just took a lot of the fun out of the game. When you go to safe houses, it's enjoyable to read what's written on the wall and to pop heads off zombies from a distance. Call me gay, but it's like Miley sings. It's not the destination, it's the climb.
If you are a zombie fanatic, this is a must have. For any other first person shooter, you need to try this game.