Nifenegger has a great mind, there is no doubt about that. She knows how to weave a plot together, how to shock in the most intelligent of ways. But in this novel I found the characters undeveloped (except for Martin, I loved his depiction, though I'm not sure what that storyline had to do with that of the girls) and more to the point they were, almost all of them, unlikeable. I couldn't understand the motives behind their behaviour at all.
The story becomes very dark, so much so that it made me uneasy. And yet I kept reading. Perhaps the author is saying: you may dislike these characters and find it hard to understand why they do what they do, but what does it say about you that you are still reading, that you derive enjoyment from this darkest of stories?