Although my pre-ordered copy of Revenant Gun arrived a while back, I took the time to re-read the previous books (Ninefox Gambit and Raven Stratagem) before tackling this one - it's a bad habit where series are concerned, as it cuts down on time available to read new stuff, but at least I know the quality is guaranteed!
As before, it helps immensely if you've read the previous books because Revenant Gun is all about the fall-out from Cheris and Jedao's actions as they try to replace the hexarchate with... something. In this book we discover that there are actually two somethings in competition to be that replacement, a Protectorate run by General Kel Inesser that seems to be trying to restore the previous order and the Compact, which is going in a completely different direction. The latter is run by the unlikely combination of Kel Brezan, former crashhawk turned unwilling politician, and the one remaining hexarch, Shuos Mikodez, since Cheris hasn't stuck around to get dragged into the day-to-day details of replacing the system she helped overthrow.
Anyway, at the start of Revenant Gun, we discover that Mikodez is not the only hexarch in town after all - his nemesis Kujen is still around and wants to turn back the clock and reinstate the hexarchate. His main weapon for this is a version of Jedao he's created with a scattering of the general's memories, who he then puts in charge of a new Kel fleet - even when Jedao starts to demonstrate he's got a mind of his own, Kujen doesn't really seem to get the danger he's in but functional immortality will do that, I guess.
Meanwhile, elsewhere in the storyline our two replacement states form an unwieldy alliance and Cheris is also off scheming to try and kill Kujen, so much of Revenant Gun is played as a three-hander and you need to pay attention to keep all the storylines straight. At one point, Cheris and Jedao run into each other again and it doesn't go well - for Jedao, anyway - although it does reveal a significant plot point about who this version of Jedao actually is.
All in all, Revenant Gun is another great read and I definitely had a couple of moments where I went 'what the hell?' as something was revealed or things worked themselves out. Much like the previous volume, a lot of plot depends on the idea of the Kel formation instinct - something that forces Kel to obey their superior officers no matter what, unless they're crashhawks like Brezan - and the uses (and abuses of that) with tragic results for some at the end of the day. Anyway, no surprises that I loved this book and look forward to seeing what comes next from this author!