I just got back from seeing the American and it was startlingly good. I must admit I didn't expect much going into it other than that the idea of George Clooney as an assassin couldn't be bad. What could have been another fast-paced, Bourne-style shoot-em-up, ended up being something else entirely: a slow-paced, deliberate thriller; practically bereft of dialogue, yet mesmerizing.
This type of assassin film like Leon (aka The Professional) isn't about a man who kills for a living, it's about an artist, a master. These films are about a man who has honed his craft so well that it has swallowed him whole, such that he has no life beyond the work except perhaps a single antithetical hobby (with Leon it was old movies, with The American it was butterflies). The assassin/artist remains locked in this life of endless mastery of craft until he is snapped out of it by an outside force, a woman.
The American follows the old tropes well, but it does so in such a deliberate manner. There is nothing wasted in this film. Every line of dialogue, every shot, is loaded, but subtly so. This is not a film for those with wandering attention spans, The American demands your attention just as much when it is saying nothing as it does during the few true action sequences. In the end this is a movie for critics and film students though. The average moviegoer is unlikely to appreciate the artistry of a film like this. Even when Tarrantino does "deliberate" and "methodical" he's usually doing it while cramming a ton of dialogue in the scene. Watching The American is at times like reading a comic book without words, it's the same art form, but it requires more from the audience and the filmmaker.
I don't know quite what to compare this movie to. It reminds me of Leon in the basic theme of the assassin, but has far less outright action. I suppose it invoked images of The Third Man, yet even that's not 100% correct although as far as correlations go it's likely more apt. At any rate, if you're looking for something different and you like this brand of assassin fiction as I do, then you owe it to yourself to see The American.