The purity, the obsessiveness, the almost solipsism of the narrative voice that drives this book is some of Levithan's most gorgeous writing, but I think the way the story was composed ultimately lets the story down.
When I read, in the postscript, that his photographer-collaborator had sent him pictures one at a time while he was writing and Levithan improvised the story around them on the fly, it crystallized my niggling dissatisfaction with the book: nobody besides Ev seems like a fully-realized character, with a reasonably coherent set of motivations driving their actions. Everyone else is a cipher: not just because Ev can't know everything there is to know about another person–this would be yet another expression of the central theme of the novel–but because it doesn't seem like anyone
knew what they were supposed to be thinking at the time that any given scene was written. This is particularly evident in the spectacularly unexpected (and for me, unconvincing) dénouement.
Obviously, though, I liked the book more than I didn't like it.