So, book three, The Stone Sky, won both the Hugo and the Nebula, putting it in a very select group.
This is odd because its one of the very rare books that achieved this with a sequel that didn't have a previous installment on the list.
But regardless, my experience with that short list in particular is that the books tend to be very politically slanted. I'm not sure the book deserved its position by its own merits, but I think its definitely something that politically/culturally fits for the times, and therefore appearing on the list is reasonable .
IMO, the first book was the best, then the last, then the middle. This is a common trend I'm seeing with trilogies, and something I've come to expect.
The very end was touching, if predictable, and I agree with H that the worldbuilding "past" stories from Hoa ended up being more interesting than "current day".
There's definitely great commentary on the nature of subjugation, racism, and institutionalized violence/hate. Commentary that was built into the world, and not highly visible from the start, making its way into later books once the ground was set. The first book had the most interesting exploration of magic, despite later books adding in new layers, and I found myself wishing for some more involved Magic Duels. But magic wasn't what the book was about, and I think largely Jemisin accomplished what she set out to do.
Its a quick read, compared to some of the other books I've been reading, and I'd definitely recommend it to anyone on the fence. Its a great fantasy story.