I... have no idea where to start. Except to give the warning I've been giving to others since I started reading the book. Which is to bear with it. To be explicit, bear with at least the first 25 pages. If you think you can't handle it after that, feel no shame. This book is the definition of something that is not for everyone.
Here, I'll help. This is a book about a family of freaks. Specifically, the parents in this family worked their darnedest to produce children with physical abnormalities. They owned a circus, and needed performers (although I don't think that's the entire reason they wanted a family of freaks). The novel's plot revolves around one of the children, her childhood in the circus, her relationship with her extremely twisted brother, and the life she had many years after the circus.
My problem with the book isn't the plot. That is actually somewhat standard - complex familial relationships, personal growth and understanding, a little bit of a mystery, and some form of closure. It's the strange assumption that what we are reading is normal. Well, not so much normal as "to be expected". That this odd world these people live in is playing out right now in the American heartland, and this book just showcases it. I don't think that's all of it, though, because the ending to the novel does recognize the apparent "wrongness" of it all.
I expect Dunn does this on purpose - hides her own feelings for this world she's created. Except, I am uncertain what kind of take-away she wants me to have at the end. Having read about her life, it feels as if she'd welcome a real-life example of this, and be giggling with glee at the discovery.