You've watched the trailers.. you think you know what the movie is about.. but you don't. You THINK you know.. but you don't have a clue. I didn't. There's no way they can describe it in a trailer, so they had to show all the money shots using the effects. The result is absolutely mesmerizing.
I can't imagine how Chris Nolan was allowed to make it. There's no way a studio was convinced to put so much money behind a project like this just from the standpoint of its concept. He HAD to have bargained to make it for doing The Dark Knight. Spielberg, Cameron, Nolan... seriously.
Go see Inception.