Even though the original Assassin's Creed was a fun game, and one I spent quite a few hours playing, I wasn't truly hooked on the idea until Assassin's Creed 2. It improved upon pretty much every aspect of its predecessor. The story was far more interesting and the main character actually likeable, the world was way more detailed and practically begged you to explore it, while the addition of new tools and gadgets made all of the climbing and sneaking around finally fit together.
So if you haven't played Assassin's Creed 2 and you currently have a bit of free time, consider yourself quite lucky as Ubisoft is giving it away for free right now. All you need to do is head on over to the official website, claim yourself a copy, and you'll be roaming around Florence in no time.
That said, time is a bit of a limiting factor here given that the giveaway will be closing down in one day, on April 17th. The good news is that you don't need to install or play through the entire game in a single day. Simply claim your copy and you'll be able to play it whenever you want.
Have fun, and I'll leave you with one of the original trailers, just so you get a bit of an idea of what you're getting yourself into!