It's very low fantasy; technology is basically medieval, with the exception of some cannily low-tech elevators and vent shafts.
The dwarfs (spelled that way consistently because I'm a contrary jerk) are actually the only race living in the entire world. While they're essentially used as the stand-in for humanity in terms of the story, they're also extremely bizarre, and have their own unique culture I drop you right into like an anthropologist. If you're expecting Tolkien or HARD DRINKIN HARD FIGHTIN DORFS, you're not going to find it here.
The world itself is one where the entire surface is a mountainous wasteland, plagued by inconsistent seasons, months of total darkness, and extreme weather that chokes out most plant and animal life. Because of this, the dwarfs all live inside the mountains, and can only go up to farm greenery when their area of the world is not experiencing a season of darkness. Mountains--and the greater Ranges they support--are therefore forced to collaborate with one another to produce and trade food, and it's only by doing so that the whole race can survive.
Society is basically a kind of soft communism, where dwarfs "loan" a week of labor to the mountain in which they live, in exchange for food, shelter, all basic amenities, and a small wage, to spend among their fellow dwarfs. Everybody has work, and all work is considered critical.
And if you don't do your work--or if you, say, kill someone--they remove you from the equation. You're banished above the ground to earn your survival alone. The more heinous the crime, the longer the sentence. And you can only come back inside while the bells of a certain yearly celebration are ringing. Miss your bells, and your sentence repeats...
...and that's where the story starts: with a dwarf who's been living alone, above the ground, for over forty years.