Tsutomu Takahashi is an extremely underrated mangaka. His works have only the smallest of niche followings in the west. This is in spite of the fact that not only did he mentor Tsutomu Nihei (who is much more famous than he is), he has produced a very large body of work over the years; unlike some artists who stagnate, relying on their old franchises and/or having any new projects be very underwhelming, Takahashi has arguably only gotten better and better over time.
Skyhigh is a short story anthology that focuses on people who were murdered or who have lingering feelings of resentment. The Guardian of the Gate of Grudges, Izuko, offers them three choices: they can go to heaven and be reincarnated, they can choose to roam the earth forever as a ghost, or they can possess someone and go and kill one person, at the cost of being sent to hell for all eternity.
Skyhigh is a seinen manga, meaning it's aimed at an older male demographic. As is typical of series in that demographic it's relentlessly brutal and griml. The stories are very often extremely tragic, featuring graphic violence and sexual content that really shows the dark nature of humanity. Often the people who end up at the gate are so full of hurt, rage and bitterness that they are unable to let go and end up choosing the third option, but the stories where the characters choose the other two are made even more memorable in light of this fact.
Skyhigh is a very good example of how important the art is to a series. The stories, by themselves, are decent and have good ideas, but it is Tsutomu Takahashi's exceptional draftsmanship and storytelling that brings them to life and gives them their power.
This is an older work of his, dating back to 2001, so it is not representative of his current ability, but even before I saw his more recent work, I was still very impressed by the art in Skyhigh. Takahashi has a very unique, instantly recognizable style, often referred to as being "sketchy" due to his frequent use of thin lines and thick blacks. This in no way is indicative of laziness or lack of talent however, it's merely a set of stylistic decisions. Indeed, Takahashi is much more skilled than the majority of mangaka; all of his characters look completely distinct, and his facial expressions are incredibly powerful.
If I had one complaint to make is that he goes a bit over the top at times, which in retrospect may make it hard to take the darker moments seriously. But that's pretty damn subjective.
Overall Skyhigh is a great read if you are looking for something dark and different with amazing art.