That game was the last time I cared about any AC game, and I always thought it was somewhat underrated. Mechanically, it's the best of the Ezio games. I don't think it gets enough credit for that. It reached a good balance where parkour had a lot of tricks to it, so it felt truly fluid and your ability to move around wasn't impaired by clunkiness. But at the same time, it wasn't fully automated and still required some level of input from the player. It was also the only time in those games were I felt like stealth was something worth trying, with all the bombs and gadgets you get.
I don't really remember anything about the story though. Even playing it at the time it seemed to wash over me without anything really sinking in. It wasn't for it being too close to Brotherhood either for me. I was already starting to feel the burnout on the series by then, and so I stalled on getting around to Revelations until quite a while after it came out. And then even as I was playing and enjoying it, I already knew I probably wouldn't be able to stomach any more of the series. That has proven to be true since. And I have a feeling if I tried to go back to this one, I would probably not like it anymore either.