So, I received this book in the mail and read it in one night. I rather enjoyed it. If you've been following all of the Mirror Universe stories, it wraps up pretty much all of the dangling threads that were left hanging.
If you haven't, there might be some subplots that you might feel a bit behind in, but they do try and convey what everyone's background is. Spoiler
So, the Terran Rebellion, the leftover Romulans, and Memory Omega team up and with a shipyard at a secret base, make Picard their military leader. This leads to liberation of the old core Terran Empire planets, and instigating a war between the Cardassians and the Klingons, until both sign non-aggression pacts with the Rebellion, making it a legal government. Eventually, we see enough wrap up to see the Rebellion rebuilding to become the Galactic Commonwealth and them becoming a figure on the galactic stage.
So, if you've been enjoying the Mirror Universe stories, pick it up, it's quite a fun read, and gives us a proper ending to the entire series, while leaving room for a sequel.
It was certainly good to see Mac Calhoun being a magnificent bastard (as usual), and I liked how he was able to maintain his autonomy from Memory Omega. To explain, it sometimes seemed like Memory Omega was another unbeatable resistance/secret society, mostly because of its Vulcan agents being capable of ranged telepathy (the potential of which we see when they finally make their move against the Alliance). As such, I liked that Mac had some protection from it in the form of McHenry, meaning they had to actually persuade him to join up (via Picard) rather than just brainwashing him into obedience. It also shows that Memory Omega aren't a bunch of arrogant know-alls, or at least Tuvok isn't since he suggested they admit their telepathic capabilities to Mac rather than attempting denial, which he would take badly. Keiko, having been out in the galaxy, also forces Memory Omega to face up to the situation instead of blindly following Spock's plan letter for letter. They return to form somewhat with the establishment of the Galatic Commonwealth, maintaining themselves as its protector and threatening anyone who dares challenge the GC with Genesis torpedoes. I can't help but think they might get a little too big for their boots and end up threatening the very democracy they profess to be protecting, which would make an interesting sequel.
One complaint, from a personal perspective, was how they dealt with the Cardassians in the end. They had Tekeny Ghemor, the Emissary in this universe, visit a guilt-ridden Damar and persuade him that the Oralian religion (of which he is a secret adherent) is the solution to all the Cardassian race's character flaws. The 'spirituality solves everything' ploy generally sticks in my craw, but then again we never find out what happened after that, so there's no guarantee it'll actually work.
Throwing the Dominion in at the end was a nice touch.
I felt the Dominion part was a sequel hook. But we'll see.
As for the Cardassians, it's more of a return to form, considering that beforehand, in the main Trek timeline, while certainly not saints, Cardassia was nowhere near as bad when they had their religion, it was when they purged it that they became even worse. Also, you're right, Ghemor brought two proposals to Damar, the non-aggression pact and the return of the religion. We know that only the former happened conclusively, and that's more than likely due to their very weak military.
The Galactic Commonwealth is still in the midst of rebuilding everything, and that seems to be the focus of their entire government when we leave them. Considering that every power around them is rather torn down, beat up, or conquered, they have a rather nice opportunity to come into the galactic scene. Well, aside from the Tholians and the Breen, but they seem to have good relations with them so far.
