As someone who has not watched the anime yet, you should probably go watch it over reading this adaptation. The reviews on Hell Girl's manga page should be taken into consideration as well.
So the question is, is this manga horror or a comedy?
The way the manga presents itself is very childish; even though there are serious tonalities in every chapter. The theme of Hell Girl is supposed to be dark, and the artwork did not deliver that. You have panels that did not transition, and sometimes you don't even know what the heck just happened. Also, for some reason 90% of the chapters open with a character making this face expression =[]= and for what? To relieve the nonexistent tension in the manga? The exaggerated faces make it feel like you are reading a comedic manga. There are people who have complained in the forums about the artwork being “too shoujo”, which, in the end the artwork does not translate well with the context of this manga. The art is cheesy, especially when a character is being sent off to hell. You can't take this manga seriously. Someone like Junji lto should've taken on this kind of project, or anybody that's experienced in horror manga art. If there are “complaints” about this manga and style being “too shoujo”, would this manga do better without the “shoujo” aspect?
Each chapter is formulated with the same type of female character with repetitive plots and outcome, and barely shows diversity for potentially different scenarios and (male) characters, EXCEPT for the last arc of the manga. If it's supposed to be like this in the anime, that's fine and all, but this is just a criticism I have as someone who has not watched the show. It makes me wonder if this repetition translates better in an anime format.
What was also weird to me were the many comical panels at the end of each volume. It's purpose is to probably make fun of the "seriousness" of the series, but it didn't really fit in, given how everything else is portrayed in the manga. The artwork is already comedic enough where it already feels out of place to add comical panels at the end of each volume.
This is not an adaptation I would recommend, especially if one is an avid horror fan. It was hard getting through the first half of the series; it eventually picks up around volume 7 where it felt more interesting to read and the artwork was tolerable; to a point.
All and all, this manga is not worth the time and energy. The artwork and context do not blend well in manga format.
Again, I highly encourage you guys to read the reviews on Hell Girl's page to better understand why this may not be a good adaptation. Please go watch the anime instead.