The Syndicate half of the guard/prisoner relationship which was mostly background in the previous series is active in this novel (Colonel Rogero), but while he is important, he is not central. The central characters are Iceni (mobile forces) and Drakon (ground forces). They are each independently moving to liberate the Midway star system from its oppressive Syndicate hierarchy, partly to advance their own interests, partly because they actually have a moral core and don't like the way the Syndicate does things. They stumble upon each others efforts, coordinate, and succeed -- which isn't really giving away any of the story, because the story is about what to do after the revolution succeeds.
Some of the events of the most recent (IIRC) Beyond the Frontier series (when Jack Campbell faces off against an Enigma fleet and a Syndicate fleet at Midway) are just starting to occur at the tail end of this book.
Black Jack Geary is such a huge figure, and not just within the Alliance, that a large chunk of the Lost Fleet series is about the repercussions of _being_ a Hero. Drakon and Iceni have small amounts of the same thing going on, but while they both have a strong moral core for their time-and-place, the Syndicate's ethical structure is so wildly Not Like Ours that in some ways they feel like anti-heroes. Anti-heroes groping for redemption, but still. The primary theme developed in this context is the downside of doing everything to be Secure. While you could make the case that Campbell beats this particular drum a bit stridently, he does some really interesting things with it that I found thought-provoking.
I'm looking forward to the next entry. I can't believe I'm saying that, but I am. Campbell/Hemry has done a lot to keep this universe feeling simultaneously lived-in (with enough day-to-day to make it Real) and fresh.