Oh, I adored this book. It was The Wizard of Oz and Alice in Wonderland and Coraline all in one. Valente is an excellent narrator with a sure grip on the cadence of Victorian storytelling, the art of the fairy tale and the narrative voice of young adult literature. She's pitch perfect throughout the story.
The Girl... is one of those books that knows all the tropes and puts them to great use, often at slightly odd angles to the way in which one is used to them. Having read Baum, Carroll, Gaiman and other masters of the children's fairy story, I can appreciate just how great a handle Valente has on her material and just how deft a touch she uses in making it her own.
I haven't read a book that I would describe as "perfect" in a while, but this definitely qualifies.
Alright, I'm done gushing now.