The original story is one of existentional horror and psychological dread. This new take on the story adds another layer - the visual, grotesque horror that is only hinted in the original. This is where Junji's craftmanship truly comes in play, as the depictions of "ghosts" and the humanity throught the eyes of the protagonits are truly chilling. This is Junji's first major work that doesn't use the supernatural as a source of the predicament and this change was a great succes. Otherwordly illustrations of inhumane horrors that come from weirdly familiar human source are, after all, from source closer to a reader and can hit closer to home.
Of course, the horrors aren't the only way the illustrations help with conveying the story. What I really liked is how the character design reflects the character itself and their background. This can be most easily observed with Tsuneko and it's amazing how just a small difference can portray the depression, tiredness and worn-out lifestyle through her face.
Back to the story portion of the manga. The core of what makes the original story great is still present, so I would like to focus on what is different and new in this work. Some say that the additional bits that Junji added are too violent and don't fit the naration. I disagree - violence is a part of human nature and the one portayed in this manga is well within the real possibilities. I could go even further and point out that using a reality of violence commited by humans in a way that makes the reader feel like it doesn't belong in the world brings the reader closer to how Yozo felt about humanity. I also found the little twist at the end that nods to the circumstances of the publication of the original novel a great idea.
Now, I have mentioned that the novel and the manga should be judged separately, but one can't escape the thought of comparing those two. So I would certainly suggest that you should read both this and the novel. It's up to you if you want to start with the adaptation of the original, though I'd say that reading the novel first and the manga shortly after while your memory is still fresh would be the best to enjoy both of those works to the fullest. You should also check out the manga by Furuya Usamaru which is yet another interesting take on this story.
And finally, some notes about the official English release. I really liked how Viz used the English release of the novel as a reference point, so the feel is so similar and frequently the exact same phrases appear, helping the transition from novel to a comic. The English cover is also very aesthetic and overall feels good, so if you can, you should definitely get the omnibus release.
