If you want a spoiler-free review, here it is:
Keep in mind that this is only my opinion. You'd be better off reading it and then judging it yourself if you're still not sure after reading the reviews.
Story: 2/10
The story might have started off good and interesting, but after first 40 or so chapters it started to get more and more disgusting, not that it wasn't already. The whole "life and death" game scenario was actually kind of interesting, but then the story deviated from that and basically turned into a horror, gore, tragedy.
Characters: 4/10
All the characters except for the male and female lead were pretty f***ed up in the head. Hell even the male lead has issues being I don't know a NORMAL HUMAN BEING ? Only character that I really actually liked was Mashiro. The other characters do have a sense of individuality, but they're not the likable kind. Even the MC is half-baked.
Art: 8/10
Although I found the story disgusting, the art is actually pretty decent. Probably one of the only things I liked.
Overall: 4/10
I've always been a gore and horror fan. And I can usually tolerate rape when it comes up. However, when every single arc is based around rape, murder, and then repeat, it gets not only repetitive, but also disgusting. The art and the whole life death game is the only thing that stopped me from rating this even lower. But hey, if this is your kind of thing then go for it. It's definitely not mine.
TL/DR:
Starts interesting but turns into trash. Art and life and death story line is only thing it has going for it. Everything else is sh**. Every arc is filled with rape, murder, and gore. Don't read if you're looking for a Life-Death game type manga as this isn't worth reading for solely that.