Central to the story is “the machine”—a world-sized mechanism so vast that no one is familiar with more than a few sections and so old that its creators, even its purpose, is lost to history. The machine provides all that one needs to live, and, to some extent, all of society lives to provide for the machine. Marrow’s Pit is a hellish central deposit area that takes all discards, organic and inorganic and somehow processes this matter to feed the machine itself.
Interestingly, and as noted in other reviews, the machine is not so much part of the plot as much as it creates the setting, the landscape. Some were disappointed, and I understand this feeling, but for me all stories, whether sci-fi or horror, or any genre really, are about the people---because human nature never changes. I found the story riveting and the world-building first rate.
I hope that this is only the first story of this dark and fascinating world. I feel that we have not even scratched the surface---the world of the machine would easily support a whole series of compelling novels and novellas.