Plot/Story
The writing is good, there are some plot twists and it gets confusing at times but overall its great, it has funny moments and other moments where the determination of the main chatacter is shown, a decent balance between both in my opinion. And well, as expected from Tatsuki Fujimoto, there are some fairly odd and weird moments. There is some gore and a LOT of burnt people, just with the title of the manga you can guess why.

Characters
The main character are great, their personal development is good and the main character's progress from pain to understanding and showing of willpower is weirdly encouraging.
Secondary characters are definitely not as good, the villains are a little bland and are really similar, but I do find it interesting that the line between villain and ally gets blurry at times.

Drawing Style
Tatsuki Fujimoto has a great drawing style, but particularly in this manga, it gets hard to comprehend some scenes and panels, but its not much. The two page panels are amazing and the fight scenes are quite cool.

Enjoyment
It's an enjoyable manga, it gets really dark at times but If that's what you read, go for it. The drawing style is good as well as the story.

Overall
Great drawing style, good story, bland enemies, its more like a fight inside the main character's head, which I guess its also good. Dark at times. Good read, I recommend.