One of THE best stories ever put into a game. Plus the amazing combat system.
The Combat is prefect, as well. With many moves and counter attacks, you'll never get tired of watching Altair shove his sword through another gut.
There really isn't anything negative, other than the somewhat repetitive missions, with the exception of a few. I wanted to start another campaign and unlock some of those pesky acheivments, but instead found myself thinking it better to wait until the new release of the sequel.
I also wish they would have taken that extra step to make it multiplayer. But that is coming in the sequel, as well.
If you haven't tried this game, but it or rent it. NOW!