There has been significant discussion in the speculative genres in the last few months about grimdark, grim, dark, and various other combinations of adjective that circle around various shadings of meaning related to books in which many, many unpleasant things happen.
Ian Tregillis doesn't seem to be the sort of thing they mean, but lordy, do many, many unpleasant things happen in his books. So very many that I wanted to read about pandemics for a bit first because it would be less upsetting. And yet it's all quite well done, so I was pleased to get this book and eager to read it--just, you know, prepared. Braced for it. In the right mood.
It's very hard to review the culmination of a trilogy that's structured like this one. Not only the emotional impact of this book but the very basic outline of its plot points are immensely dependent upon the events of the first two books. Most of the things I could say would be spoilers just from page one--and meaningful spoilers, spoilers that would decrease the impact of events for first-time readers.
What I can say is that this book does not fail to follow through on the first two. It maintains continuity of tone and structure and yet achieves a limited redemption for some of the characters. The light at the end of the tunnel may be one of those hand-crank flashlights that you have to work like hell to get going, but it's not the oncoming train. The world of Tregillis's trilogy turns out to be very like the world of Pandora's Box: full of all manner of nasty things, and also, at the end, hope.