The premise is that faster than light travel is only possible for space ships if they enter "the Flow" at specific points and exit at specific points, like getting on and off one way buses at specific stops. The ruling house of the Interdependency maintains control by granting monopolies to specific guild houses who must produce their goods on specific planets. Thus, one planet is dependent on the monopoly goods of another planet and vice versa. And the ruling house of the Emperox collects tribute from all the other houses/planets because they control the hub of the Flow, the "central" location where most trade has to transit.

OK, so that's the setup. However, a Flow physicist on an outlying planet has figured out that the Flow is collapsing, which means that every planet has to become self sufficient beforehand. Or die.

Can the physicist get word back to the Emperox before someone else takes advantage? What if the Emperox is a bad person? What if the local duke on his backwater planet kills him first? What if the bad guys all have extremely mustache-twirly plans that the author takes great pains to make obvious to you the reader so that who is doing what is never in question and instead the only thing you have to wonder about is will the good guys execute their scheme in time?

Also, what if everyone talks the same way? What if they all start off every conversation with some diplomatic language and then a minute in everyone says "let's cut the shit and talk without pretense" and then they do.

Anyway, for once, I enjoyed a Scalzi book. It's interesting even if it's pretty shallow.