This is the sequel to Ancillary Justice, and if anything I enjoyed it more than the original. The world is already set up, most of the hand-wringing over being a sole fragment of a large AI system has been done, and we can get on with things a little.
While the whole set-up feels like a book with Big Action, not a lot of Action happens. It's mostly politics - having arrived in a new system in the middle of effectively a civil war, how to bring stability, clean the place up, work out who to trust, etc. Somehow, this actually works, and isn't tedious. Underneath this the backdrop of the Big Political Situation, which evolves but is nowhere near resolved in this volume.
I think it all hangs on the viewpoint character. As an AI who isn't quite human, but is linked into the pervasive sensor system, she can justifiably spend lots of time going on about other people's emotional state and working out the intrigues going on in a way that would feel leaden with a human protagonist, and allows cutaways to other characters without actually breaking a tight first person point of view.
The society structure in the book, being based around a certain amount of good form and hiding of emotions (and evil), also lends itself well to this. While not choc-a-block with pointless misunderstandings, mistrust and attempts to interpret emotions run throughout. This could have been deeply tedious, but it was handled well.
Looking back, it's not an obvious big book of fun. It's perhaps a political thriller, at actually quite a back-water level after the big bangs of the last book. It's permananently dwelling on the emotions of those involved. Yet someone I found this really engaging and enjoyable.