The further adventures of Miles, after graduating from the Academy.
Immediately, he's given a post: as a Meteorology Officer. Which seems like an awful mismatch, and he gets told that unless he manages to pull off subordination better, he's not going to manage in the service.
Things don't stay simple. At first there is simply the matter of trying to learn to lead the less than clever soldiers, and manage to obey the commander (obviously shuffled off here) but then the commander raises the stakes -- even though Miles could ignore it.
which sends him off on another tangent, involving deep space. Also involving an overly opportunistic mercenary captain, a depressed emperor, a security officer posing as a bodyguard posing as a tourist, an attempt to space two characters, Miles making an offer, and later making a threat, that both turn on his ability to claim the throne and much more.