It is certainly compelling. It is mostly about relationships. I mean, yes, the plot revolves around enslaved gods and politics and revenge and MASSIVE AWE-INSPIRING POWER and people and gods treating each other VERY BADLY. But mostly the book is about how the characters interact and feel about one another.
It strikes me that most of what I said about the plot of The Hundred Thousand Kingdoms applies to Warbreaker too. Except that pretty much all the characters in Warbreaker, including the villains, are less cruel. Even the torture in Warbreaker doesn't feel as vicious. Moreover, The Hundred Thousand Kingdoms is much more interested in the relationships than in the mechanics of the plot. If you want passion and intensity -- of hatred, love, lust, fear, etc. -- Jemisin's book delivers a lot more. If you want to marvel at the way the pieces fit together in the end, Sanderson's excels.
Oddly, while I generally think of myself as caring more about character interactions than story, I enjoyed Sanderson's book more. Perhaps I am burned out on passionate intensity. Also, The Hundred Thousand Kingdoms includes a Dark Brooding Powerful Ridiculously Sexy character to whom the female protagonist is Inexplicably Drawn gosh where have I seen this before oh right HALF THE BOOKS I'VE READ IN THE LAST TWO WEEKS.
... yeah, I might be burned out on passionate intensity.
If I'd read this two weeks ago, I might've given it a 9, but instead I'm sticking it with an 8. Well worth reading, certainly.
And now I am going to read something light and cheerful and different, like maybe a Sherlock Holmes story.
... yes, murder mysteries are comparatively cheerful. And at least I can be reasonably assured that Doyle will not rhapsodize about how sexy his characters are. c.c