It's all of these things, yet it still could have been better. The picture constantly walks a fine line between a thought-provoking thriller and one big clump of chaotic confusion. And it often crosses the line too, as it does in the ending sequence. It's a good film, one that I'd guess has dropped in quality since showing on the big screen, but one that will still have you thinking about it long after the credits have rolled. To see a movie of this genre in the A-grade range, rent 1995's The Usual Suspects.
Memento is told backwards.
The picture slowly goes blank and then jumps back into the camera. As we move along, we learn how Lenny seeks revenge on his wife's murderer. Throughout the duration of the film, the scenes are shown as if the main character is constantly backtracking, with Lenny's voice narrating the actions and keeping us up to speed. There's one big catch to all of this, though. During his wife's attack, Lenny was struck too, and that injury has left him with no short-term memory.