There are people out there, and I bet you know at least one, who believe that fantasy fiction is simply genre fiction. That it is, to borrow a phrase that appears in movie reviews by people who do not read or watch fantasy very often, little more than magic and Morris men. (I've only ever seen Morris Men in Terry Pratchett, btw). These people are stupid. But you knew that. What you should do is direct them to this book.
LaValle's novel is on one level about marriage, about parenthood (fatherhood in particular), race, and class. It is an example of literature, of pointed societal conversation, of a love of books. On the surface the story is about Apollo and how he becomes a man and eventually a father. It takes a bit for the plot (and title of the novel) to kick in, but when it does, it does. The build up is, in fact, excellent writing. Reminded me a bit of James Baldwin.
When the title takes hold, the book becomes literature and good fantasy. LaValle does not disregard or drop the issues that he raises in the beginning but incorporates them in the fantasy narrative, which is what good and excellent fantasy does. Apollo's pain and uncertainty as he struggles to find meaning or sense out of what has happened are real, are heart rending.
Seriously, just read it.