I was not that familiar with Constantine, before this. I do slightly remember a somewhat boring movie with Keanu Reeves. I was pleasantly surprised by this though.
The film follows a magic user, John Constantine. He has to rescue the soul of his friend's daughter, who is in a coma, with her soul captured by demons. That's the basic plot. There are a few subplots too, that he has to do, in order to accomplish the basic plot.
The film is very adult. There is sex, nudity, tons of horrific murder and gore. The demons in this are the stand out part. Their world and parties, are insane. The one demon has a swimming pool full of dead bodies, that he swims in. In some ways it's reminiscent of Clive Barker's depictions of demons.
Anyways, a bunch of stuff happens. There are alot of cool secondary characters, particularly the females.
I strongly recommend it for anyone who hasn't seen it. It isn't super hero, at all. It's basically an animated horror series. I wish there were more Constantine animated films. There are a couple of Justice League films with Constantine in them. I've seen Justice League Dark, which has a heavy focus on Constantine, and is decent. It isn't the same level as this one though.