I personally really enjoyed this movie, but was disappointed that it didn't do well at the box office. This movie I feel is under-rated. The problem with this movie is that it may have been too spiritual for american audiences, but I thought it included a enough of a scientific point of view that it made it interesting. The story itself is pretty good and should keep most science fiction fans interested.
The movie itself features some scenes of violence, the overall theme of the movie is pretty mature and premature minds may not get some of the concepts. Ghosts or "phantoms" travel around the barren world of Earth and humans survive, hiding in barrier cities that keep the phantoms from consuming their "bio energy" nicknamed "souls". The violence in the movie is not graphic, but may be disturbing as many civilians are slaughtered by phantoms and there are some conflicts between the human factions. There is one kissing scene in the movie that lasts for a prolonged moment, but is still very mild. Other than that there is only very minor suggestive sexual themes, one character jokes about a machine causing him sterility as he expresses his want to have kids some day.
This movie isn't for everyone, but keep an open mind and you might enjoy it.