This is a novel at the mercy of the blurb on the back cover. 
 Many people seem to feel that it's a bait-and-switch -- the blurb promises one thing while the novel delivers another and they feel misled, which, for them, is a strike against the novel. I can see where they are coming from. 
 "Boy, Snow, Bird", despite what the blurb states, really does not read or function like a re-telling of 'Snow White'. I can absolutely see similarities between the two and you can see how, possibly, Oyeyemi was inspired by the fairy tale. If the author's intention was to craft a re-telling of 'Snow White', well, the novel didn't work on that level. 
 For me, though, I found this lovely and poetic. It felt poignant to me. I loved Bird as a character. She was interesting and familiar; she felt lived in and the section of the novel narrated by her was my favorite part. Boy, I went between being infuriated with and being charmed by her. 
 Snow? Snow is a bit of a cipher and I think it works as this is what she is. She is an unknown quantity to Boy and to Bird, she's the 'never seen-often spoke of' elder sister. 
 The only bit I really have an issue with is the last chapters where the transgender issue comes up. I have no problem with characters in the novel calling it a mental illness, as this book is set during the 50s and, quite frankly, that is how it was seen. My issue is with how it manifests as a response to a trauma. That....I don't know what that was about. There's not enough there to make it understandable, if it was meant to be deeper than what it seems. 
 Even so, I quite enjoyed "Boy, Snow, Bird" and I've already added two of Oyeyemi's works to my TBR list.