Saw is the type of movie I thought I would never enjoy. But recently I enjoyed to watch them all out of sheer boredom. Luckily for me it came as a big benefit for me. The storyline is basically a continuation of the first movie, so you don't want to watch this before you've watched number one.
From all of the Saw movies, this is my favourite. Maybe that's being a little biased as I've seen this one twice and I've only seen the other four once. In the first movie, you see John Kramer but you don't really see how much of a genius he is yet. You begin to see how clever he is in this movie as it goes on. The ending will really get you thinking as I said above, but it's a movie that would really make you want to watch number three straight after (taken from experience).
Unlike the first movie, this one has a game with a few people who were taken from their sleep and left on a floor of an abandoned house with each other. Amanda Young (who had already played the game one time) finds herself playing Jigsaw's game for the second time - or at least that's what you think!