This book is the second in a series, set in a really intricate and complex world. I would therefore in no way recommend you start with this one, and if you haven't read the first book in the series, Cold Magic, skip this review entirely to avoid both spoilers and confusion.
In a very long blog post at the start of the year, I tried to outline as much about the world in Kate Elliott's Spiritwalker trilogy, and the plot of the first book in the series, without spoiling too much of the main events.
This is the sequel, and the first chapter actually recounts the events of the final chapter of Cold Magic, something I've seen other reviews complaining about. Myself, having not read the previous book since January, I was quite grateful to be reintroduced to the world and the characters without having to pick up and reread the whole previous book.
Catherine "Cat" Bell Barahal and her cousin Beatrice "Bee" Hassa Barahal are on the run from powerful mages and all sorts of people who want to get their hands on them. Bee has prophetic dreams, that can both provide useful information to a number of ambitious factions, including that of the deposed general Camjiata (a bit like Napoleon), but also marks her out as a target for the Wild Hunt, where creatures from the Spirit World hunt down and kill people in the normal world. Cat seems to have escaped her arranged marriage, just as she's discovered that she has the potential of maybe loving her haughty but brilliant husband, has the ability to walk as easily in the Spirit world as in the normal one, and needs to discover the identity of her real father. When she does, she sort of wishes she hadn't. He places a binding on her, so she can't tell anyone who he is or what he's asked her to do, and then sends her to find a powerful magic user, or he's going to kill Bee when the Wild Hunt next rides.
The previous book was set in an alternate reality version of Europe, Cold Fire explores more of the world map, and most of the action takes place either in the Spirit World, where Cat discovers more about her heritage, or in an alternate version of the Caribbean, where the powerful cold mages of Europe have no dominion, and there are zombie like victims of the salt plague, and equally dangerous, ambitious and powerful fire mages hold sway. Cat meets her husband Andevai again in the most unlikely of locations, and slowly, while trying to figure out a way of saving her cousin and outwitting her supernatural father, comes to know and understand him better. Much more of the various political factions of the world are explored, but not that much happens in this book. The action is slow to start, there is a lot of putting pieces into play, but I suspect Elliott is mainly establishing plot points to be finished off in the last volume of the trilogy. Because I'm interested in Cat, Bee and Vai as characters, I will read the next one, but I hope it has more plot, and less "look at this shiny world I built with all it's similarities, yet differences to the real historical world".