This is one of my favourite manhwa/manga but I'll try to keep this review short:
Story: The story is very creative and I don't think you'll find anything like it. It starts off interesting already but it gets deeper as you read on. I don't think this book has a specific genre, as it's just filled with everything - from action and thriller to background stories that can be really emotional.
Art: I personally enjoyed the art a lot, especially in the later volumes. It really changes throughout the books, which is the only negative thing about it in my opinion, since it was a little
bit hard to follow, but it's definitely possible to get accustomed to it.
Character: I already mentioned that there are backstories, which are sad but really interesting. I think it's very nice that through the "Dead Zone" you get to see characters that aren't in Da-Il's daily life (anymore) again.
Enjoyment: The manhwa is written like it's the work of the character Go-Ho, which made me feel like I somehow was part of the story too. I read each volume without taking a break.
Overall: It's very well written so if you're looking for something different and interesting, you should definitely check it out.