When this was first released, much was made of the fact that all the CGI had been done by the director on a computer in his own home. Although slightly more complex than that, it is a very visual film, with one of the main protagonists a photographer.
I saw this film as a parable of fear and insecurity in post 9/11 America, with the monsters threatening the safety of the status quo. (Pretentious, moi?!)
Slow moving, but worth a look, because it’s different.