The Obelisk Gate answers some questions raised in The Fifth Season, and raises a couple more questions in turn. It isn't my favorite book out of the trilogy, which doesn't mean it's bad because this entire series is just BRILLIANT.
(Maybe I just had a hard time reconciling the Schaffa in this book to the Schaffa in the first one?)
And Jemisin sticks the landing in this one. The origin of the stone eaters wasn't exactly what I expected, the throwaway use of the word "magic" by Nassun in The Obelisk Gate is ignored, in a way, and I still maintain that Hoa Dumbledored Essun a bit. I love this book, though, and would definitely reread as soon as I've calmed down.