Perfect Dark Zero was hyped pre-launch as a "Halo-killer". The reality is that it is not. But, the comparison is unfair since PDZ is an excellent game in its own right.
The single player story lacks some depth but is unusually satisfying. The ability to "cover" by hiding behind a box or wall works well. Some levels work better than others, but there are no terrible ones.
The co-op multiplayer is excellent with two players playing side-by-side at times and taking different routes at other times. When the story branches, the two players objectives support the other users.
I have at times lacked the patience for some games in the past such as the Metal Gear Solid series, yet I find myself playing PDZ for much longer sessions than many similar games.