Its been a long time since I last watched it but maybe a couple of points.
I found alot of people (most infact) had watched it more than once - some to get a better understanding, and others for the immersive experience. My brother called the film the best he's ever watched.
I personally think that this film involves the audience in a way that other thrillers don't. All thrillers try their best to captivate their audiences. Grabbing an audience and keeping them in suspence all through the ride is what hinges these films.
The way this film involves, stimulates, and inspires its audience is by using the focal point - memory and its nature - as a basic filmic technique which directly affects narative.
The technique used in the film - whereby its cut up and has no chronological structure, I forget the name - has been used before, namely in Pulp Fiction., but in the case of this film it is intrinsically related to the characters plight. The veiwer is engaged on another level - you have to do alot of the hard work and try to piece together the ideas in the film. The confusion and anxiety experienced by the main character mingles with your own.
A film that done this to some degree is The Usual Suspects.
The film in its structure sais alot about memory and how we use it, because the viewer has to apply his own memory to navigate mentally through this film.
I don't know that's off the top of my head. Maybe some form of debate will draw you closer to how you want to articulate what the film represents for you.