Philosopher Isaiah Berlin once discussed how thinkers could be considered "foxes" or "hedgehogs". The fox draws on a panoply of things for its worldview; the hedgehog sees the world through a single defining concept. The same could be said of artists, and in that sense Tsutomu Nihei is most definitely a hedgehog. His worldview, revisited obsessively over the course of his career, is one of endless sprawling, cavernous, vertiginous spaces, inhabited by dead things that somehow live and living things that are barely alive. Abara is a one-shot Nihei story, originally published in 2005 but now released in English by VIZ in a handsome single volume edition. It serves as a surprisingly total point of entry into the man's narrow, grimy, black-and-white, but somehow always fascinating universe. If you like it, you'll like him.
Abara is, like so many of other Nihei's works, set in a sprawling city, like Prague after a dose of some mutagen, overshadowed by massive structures reminiscent of the cooling towers of a nuclear power plant. One day a man stumbles into an urgent-care clinic, shoves his spasming hand through the teller window in the reception area, and impales everyone within several meters of him with spines that explode out of his body.
The creature that erupts from the man's body, a skeletal thing that looks like a dinosaur fossil crossed with something from H.R. Giger's sketchbooks, is a "White Gauna" — a monster of superhuman speed and strength, and horrible hunger as well. A young man named Denji Itō, a grunt-worker with little in the way of human contact, may be the only one who can stop it. Itō, you see, is a "Black Gauna" — another monster in human form, with the same powers. He doesn't want to have that side of him reawakened, but he quickly realizes he has no choice, and before long he and another White Gaunta, Nayuta, are locked in a battle that may end with the whole city being consumed.
That's essentially the entire plot, with some background detail about interterritorial pissing matches within the government and the last surviving member of secret scientific societies rallying for one last-ditch effort against the White Gauna. Again, almost never in Nihei's stories does the plot matter. For him, imagery and sensation come first — bone-white surfaces jutting out of ink-black abysses, moments of brutal violence captured in 1/1000th-of-a-second snapshots. (Why there has as of yet been no live-action version of any of Nihei's material is baffling.) Abara essentially works like a greatest-hits anthology of his approach, up to and including the way Nihei ends his story. It doesn't so much end as just stop, and it stops on a note that in theory could signal the start of another story — but in practice, that other story is probably just any number of Nihei's other works. I don't know if all of Nihei's stories actually take place in the same shared universe or not, but they sure make a case for such a thing.
The few times story has mattered with Nihei, it's because he's relaxed his grip a bit and mounted a project that's meant to appeal to a slightly broader audience — e.g., Knights Of Sidonia, which not only featured a more coherent plot than usual, but friendlier and more accessible artwork. That strategy seems to have paid off, as that series found its way over here in English and even became the basis for a gorgeous, if sometimes dramatically clunky, Netflix/Polygon Pictures animated series. BLAME! was also adapted into a feature film by the same crew, but only after a high degree of condensation and reworking to be more audience-friendly in the Sidonia vein (cute female protagonist, etc.). Any adaptation of Abara would have to work the same way, I think; for a lot of people, it will end just when it seems to be getting really interesting.
On the other hand, the fact that Abara is self-contained, even if only by fiat, means it works as a good starting point to get a taste for Nihei's work in general. If you want more of just the atmosphere and action; check out BLAME! and Biomega; if you want more story and character, and a less universally oppressive approach, go for Sidonia and Aposimz.