Basically a murder "whodunit", the "Octogonal Raven" starts off very inocently, until the main character suffers a murder attempt.
From then on, the plot slowly lifts the veil of what is wrong with this future society, putting our main character under the option of sitting still and doing nothing, or trying to prevent a new colapse of civilization.
Nanotech abounds, and in the first few hundred pages the reader can be thrown slightly off by the amount of terms "invented" by Modesit to depict this far-off future, after we get used to it though, the story flows quite smoothly.
The storytelling alternates scenes between the main character's present and past, giving the reader a greater insight into him, not only from where he came, or what he has done, but also from his own thoughts and interpretations of the human nature.
A good read.