The gameplay is basically the same as in Brotherhood with a few extra features made possible by the hookblade of the Ottoman assassins. And the story is just as amazing as ever. It gives quite a bit of information that we were left wondering about after AC2 and ACB, but I won't spoil that for you. Now, there were a few things about this game I wanted to mention. Let's see if I can remember them all.
First...Altaïr's voice...I seriously can't believe they did this. This is the first and only complaint I've ever had about Assassin's Creed. They completely changed Altaïr's voice. First of all, he sounds a little bit French. And second, I realize they made a mistake by giving him an American accent in AC1, but regardless of what he sounded like before, changing it now makes it worse. I didn't feel like it was actually Altaïr, which sucked because I was really looking forward to revisiting his life.
Ah, I also wanted to mention that this game has a very unique feel to it, which takes some getting used to, but it is very cool. The reason I say this is because ACR is like a hybrid between a main numbered installment of the series (like when a new protagonist, time period, and location are introduced) and a continuation of an existing protagonist's story. We have an entirely new location with a new atmosphere, new characters, new objectives, new language, new everything, but it's still Ezio, who we've all associated with Italy for the past two years. Like I said, it can be a little strange at first, but it turns out to be quite interesting and fun.
I'll post more later if I realize I forgot something.