The entire film is played in reverse and includes out of sequence scenes, which makes following the plot rather difficult, but lets you empathise with the lead character's condition. Watching the movie at least twice seems like a must to me, to form a proper conclusion about the open-ended plot, it but the beauty of the film is, that it is enjoyable no matter how many time you see it. I highly recommend to watch this film and would suggest paying close attention.
P.S.: Remember Sammy Jankins!
Some might not be able to follow