I thought we had a topic on the first one or possibly the second Assassins Creed but I couldn't find one.
Anyway, the first two were pretty good, but this one blows them out of the water. And yes Nacho, it should be available for the PC. Basically you take over your character from the second game, and if you have played the second you have all of his equipment and money. But that doesn't matter because within the first few minutes you lose it all anyway, so if you haven't played the game before it's not a big deal. You run around 1500 Rome upgrading the city and taking it back for Borgia control. A lot of the game is exploration, similar to FO 3, but non PA. It's loads of fun and there is a modern day side note to the game that I won't go into because it's a bit of a spoiler.
It's all about sword play, quietly sneaking up on people and killing them. Massive brawls and even a little sex.