I've started watching this anime after a friend of mine recommended it to me, I've never read the manga.
Story: 9/10, not a true masterpiece but it has an interesting concept.
The whole premise of the anime is about decadence, perverted minds (not mainly in a sexual way, but also thoughts and actions that are considered evil or disgusting, a deviation from the common sense), freedom. The story itself feels disturbing but not in a gory way, but in a psychological and broken way. You must watch the whole season to really understand and enjoy what it's trying to say.
Art: 10/10
The characters' style are not like most anime. Although many people who've watched this anime simply don't like this kind of art style, I found it pretty and interesting and it really fits with the story itself.
Sound: 10/10
It also fits the story and it is, still, pretty simple. It's dark and kinda disturbing but in a positive way. The anime wouldn't have the same awkward and distressing feel if it had any other type of soundtrack.
Characters: 10/10
This anime really does have an realistic feel to it. It doesn't have an overly-skilled or magical character so you can really feel connected to most of the characters in this show. Their despair and pain is understandable and real.
Enjoyment: 10/10
From the moment I've started watching to the end of the season I felt sucked in and in many moments I felt like I've had an empty feeling inside of me (or a feeling of hopelessness/despair). I felt truly agonized (also in a good way, yes) towards the end.
Overall: 10/10
I am really hoping for a second season.