Portal 2 continues the story from the first game, but it is longer and adds a few more elements including lasers, tractor beams, light bridges, bouncy sludge and zoom goo. Now aren't you intrigued just from that list of stuff? I mean, who can resist zoom goo?
Portal 2 also has a two player co-op mode. And it is awesome. I played it through twice. That's how awesome it is. You and a friend play as two robots who have to get through testing rooms together. Puzzles that require four portals to solve instead of two are that much more challenging and exciting. You really do have to work together to get through the levels, sometimes timing things just right or relying on your partner to get you through an area. You can also interact with each other by high-fiving, hugging, waving while you careen to your death off a chasm, or pulling the other's head off and smashing it on the ground; I'm not gonna lie, there's just something satisfying about that last one. This is another one of those games that you might enjoy even if you are not a gamer, and one of the funnest games I have ever played.
If you've played Portal or Portal 2, what did you think? If you haven't, what are you waiting for?