It's really hard to explain this game without giving any of the plot away lol. You are playing through the lives of your ancestors, who are from different times in history (its pretty upsetting your friend didn't explain it to you). The Assassin's Creed series has a growing plot that is kind of like a huge inside joke in that fact that if you didn't play the first one, you probably won't get the idea of the whole series. I believe that the huge plot in the series is one thing that draws people in and also the fluidity of the game. You are an assassin in each of these titles from the series, each game linked to the ones before it, and they have each progressed TENFOLD since the previous one as well. The game series has grown since the very first Assassin's creed (it's not as repetitive, there's more to do, it's bigger, the combat is more fluid). I would recommend this game to you since it is, in my opinion, the best game in the series thus far, but maybe go on wikipedia or play the ones before to get the whole story because the story is half the fun.