The context of the book is people from various oppressed groups viewing the city through the experiences they have had there. White supremacy culture is named and held up as toxic, personified by Staten Island but pervasive in the story. If you are white, consider yourself liberal, and have not "done some work", this story is going to grate on your "ally" sensitivities (non-liberals are not a target audience for this book, and would mostly read it in order to troll it). If you've read and digested books like Ta-Nehesi Coates' "Between the World and Me" you're better prepared to appreciate the road this book is traveling.
Since I have that context I was better able to appreciate how the book was written. It's not perfect, but it's pretty darned good. The fantasy world construction is pretty thoroughly subordinated to the social justice context--see above. But the characters themselves and their stories are absolutely engrossing. I tend to read late at night and set time limits but I had a really hard time putting this one down.
One can learn a lot from this book if one is open to it, but it's not about teaching. It's telling a story very much in today's context. It will be interesting to see where it sits 20 years from now.