This book is the sequel to Lion's Blood. The story stands pretty well on its own; I think you could read it without reading Lion's Blood first and not be too confused. Both books are straight alternate history: no fantasy creatures, no magic, just an extensive speculation on what the world might be like in the mid 19th Century if the Black Death had completely, instead of mostly, wiped out European civilization and at the same time spared the Muslim world. I would never have bothered to real Lion's Blood if Heather Alexander hadn't produced Inshallah, an album of songs inspired by the story, but the songs she did from the album easily convinced me to buy the album, and the album was good enough to get me to read the book, and the book was good enough that I read the sequel.
Racial prejudice is a major focus of these books. If you think you don't have racial prejudices, reading a story where black masters are oppressing white slaves can be a good test. I think it's fair to say that if you find the reversed racial roles more disturbing than our actual history, you need to go back and examine your prejudices. There's also a lot of fascinating stuff about various African cultures and Sufi Islam, all of which feels like it's authentic and well-researched, but I must confess that I know so little about it that I can't prove Barnes didn't just make it all up. And in front of this remarkably rich and varied backdrop, we have a thrilling story with grand adventure, Machiavellian intrigue, love, betrayal, reconciliation, larger than life characters that have larger than life exploits but remain fully human so we can identify with them, and an ending that satisfies, yet clearly prepares the ground for at least one more book.
An inspiring book, well worth stepping outside my usual SF/fantasy territory. 9 out of 10.