I just recently saw this movie and it was pretty interesting and thought provoking. It's about going back in time to try to change things and how it will change the present when you come back to it.
They have two different versions of it (which is basically just two different endings) and the directors cut version is alot better and really makes more sense. The theatrical version isn't nearly as good and seemed to be made just so people wouldn't be sad about how the movie ended.