Short version: this movie is a very enjoyable film noir, with an interesting mystery story, using demons as plot attributes. It's not a demon horror action movie.
Long version: First off, this movie is weird. Not just in the sense that it's about "weird" stuff like demons, but in that it's a movie trying to mix film noir, mystery, horror, and drama. As I started watching it, I was expecting it to be some crappy demon-horror B-movie, but I've not often been so surprised (and wrong in my initial judgment). I believe the reason for most bad reviews of this movie, is that people were expecting a radically different movie. The best I can describe it is as a film-noir mystery detective demon drama. If that sounds ridiculous to you (and I can't blame you), then you're probably better off watching something different. If instead you're intrigued by this seemingly random combination of genres, you might want to give it a try.
I found the script to be surprisingly intelligent, with pretty few plot holes, and after the first "what the f*ck is this?" moment passed, I really got into the story (which I will not spoil). Most of the movie is very bleak (although it has a somewhat happy ending), including domestic abuse, alcoholism, child rape (although that was thankfully only implied, but never shown), etc., so it's probably not suited for the faint hearted. I found the acting to be much better than I expected: not Oscar nomination material obviously, but it was adequate enough. Also the special effects, being mostly the demons' body prosthetics, were quite nice. At times it was clear they were just rubber masks and floppy prosthetics, but I found the designs very elegant and was impressed with the film's visual style. Overall I would say it's very entertaining to watch and very different from what you would expect from something called "Fire city: end of days". I also found it to be thematically intriguing, and most of all a very original combination of different genres. I would give it a solid 7/10, but it gets an extra +1 because it's really much better than the 5/10 it has now on IMDb.
If you're going to watch the movie, just keep in mind you'll actually have to pay attention to the story - otherwise it's just going to seem like a strange, confusing, meandering movie. But believe me, it actually does make sense in the end. Just think of it as a film noir that happens to feature demons, rather than a demon movie, and you'll know better what to expect.
