I recently watched this for the first time, and I was mesmerized. It's the kind of movie you should go into without knowing anything about the premise or plot, if possible. It's an interesting exploration of identity. Leonard suffers from a neurological condition which has disabled his short term memory. When he falls asleep, or in moments of stress, his memory is wiped clean. When he awakens, he has to start over, with no recollection of what's happened before. In his quest to find his wife's murderer, he leaves himself mementos, photos with notes telling him whom he can trust and messages tattooed on his skin. Since he has no memory of his recent experiences and actions, starting anew each day, does he have a cohesive identity? Is he morally responsible for things he's done? This movie also has wonderful things to say about the varying reliability of memory.