I definitely rate children's lit differently since so much of my rating is tied up in how happy I am that a book like this exists for kids (and there's less space for ratings dependent on glorious flights of linguistic fancy or the book's ability to handle shocking turns because, sooner or later, most books for children will end with the main character conquering their fears and being successful somehow) and how well the author controls the mix of plot/world/character that come together to make a really good kid's book.
This was a really good kid's book. Okorafor balances the whimsy of an almost Wonderland-esque world (which she references once or twice) with serious questions about fitting in and making dangerous choices. And it's hard not to love Zahrah.