There's a lot of violence in it and it's made to look like a comic book. Which I think works pretty good in this film. Most of it is black and white, with accents of colour. They also make a lot of effective use of silhuettes. Mickey Rourke makes what is probably one of his best acts ever. :)
Over all I like it, but it's not for the squeamish or those expecting a well thought out plot. It's mostly violence in a pretty package. :D