It's difficult to describe the emotional intensity of this book. It's like when Tolkien talks about Elves in the Silm: Everyone is The Most Renowned Swordsman/Bowman/Singer/Bottlewasher/Etc. Everyone in this book is having The Worst Week Ever. The backstory is neatly summarised in the prologue in two competing documents (the SF perspective of events, and the Fantasy perspective), and then we're off to the races. The characters have already had every totally awful thing that's possible to happen happen to them by the time they meet. They're both desperate and at their worst, and within about half a page they're both pretty well in denial about how co-dependant they now are. Terrible things continue to happen at an average of 1.6 times a chapter.
So it's pretty dramatic, is what I'm saying, but I really liked how the characters handled it. Morgaine has been doing this for like a thousand years, everyone she knows is dead, she's probably going to fail, possibly causing the End Of All Things. She is the most stoic brave little toaster ever. Vanye has been living in exile, and just wants a hug, and his honour to be restored. He's very interested in honour, which is an unfortunate habit in what is basically a designated woobie.
The world building is very interesting. One of the best SF from a Fantasy perspective books I've read, with the iron-age PoV character making as decent sense of things as he can, while still letting the reader in on the SF elements. There is a lot about court politics, especially the morality of leadership and abuse of power (something the last '70s fantasy novel I read was also very interested in), and family obligations.
Definitely reading the rest of the series, though possibly after a break.