First of all, i want to express my disgust for people who bash the movie because they didn't enjoy it, or didn't "get it". I accept other people's opinions, it is a free world (most of it anyway), but please stick to just stating your opinion, don't try to change how other people feel about it.
So, in my opinion, first and foremost, if you expect a movie that has drama or action that keeps you glued to your seat, this isn't for you. The plot of the movie has nothing to do with sci-fi, war time action or drama. It is a deeply philosophical movie that appeals to the reality matrix of people, trying to immerse you into some kind of a trance, where you begin to think like the author of the book, and the main character. If you are open minded enough, or a more than average philosophical person, this movie will be quite an experience for you. I know that for me, it was.
I liked it a lot mainly because of the dream/monologue scenes, because they somehow capture the essence of human thought. The doubt, the inner contradictions, the good and the bad sides of the same person. Things that most or all of us do, maybe not in a such out-of-body experience, but it does happen.
I don't want to give to much away, because half of the movie's effect on you has to do with the fact that it catches you off-guard.