[My computer is going to be out of commission for a couple weeks, so I'm writing a quick review from the library at the university where I work. I'll go back and insert images and links later.]
The strongest part of The Hundred Thousand Kingdoms is the mythology. The gods and the mythos are the center of this story, and all I can say about them is that they're fucking awesome. And they work. Inter-weaving mortals and gods in a story is not something that's easy to pull off effectively. It often leads to gigantic plotholes and/or gaps in logic, or somehow manages to come across as not believable. (See my review of Incarnate.) But Jemisin pulls it off. Not perfectly--not all the gods and goddesses were as well-developed as others--but overall, she pulls it off.
The writing style is colorful and clever, Yeine is a great protagonist, and what little worldbuilding we see is very cool. I do wish we had gotten to see more of the world beyond Sky and glimpses of Darr, but overall, I was very satisfied with this book.
ETA: I marked this book as New Adult. Why? YMMV on whether or not it deal with NA issues, but the character is a bit younger than twenty, and the sexual content would appeal to a lot of NA readers. (I could say more on the subject, but I'm not feelings very eloquent right now.)