Sadly, I cannot recommend this game, as much as I was looking forwards to.

Pros:
- Great theme
- Funny narrator
- Good graphics
- Good performance
- Interesting concept

Cons:
- Too easy
- Repetitive
- Mechanics that turn a co-op game into a competition between team members
- Weapons that are mostly rubbish
- Gem system that become meaningless really quickly
- Character progression/skill unlock is shallow. Only two powers that really make any difference.

Conclusion:
I was personally waiting for an updated or re-imagined Zombie Sniper Elite. It was challenging, tense and fun when overcoming vast amounts of zombies. I really like the puzzle element in this game, but the replayability is low due to the puzzle mainly staying the same throughout.
The cost of DLC is ridiculous, Sniper Elite allows you to replay a level in multiple ways, which gave them value. This game can be played a couple of times (to clear any puzzles/pickups you missed 1st time) before retiring to the shelf.

Sadly, I will give the DLC a miss, unless the price is much lower or there are changes to the game that allow more replayability.