I really enjoyed this book but was pretty dissatisfied with the ending. It is a ghost story though I didn't know that when I started it. Niffenegger's characters are always engaging and interesting, though I felt this time there was one character who was underdeveloped or under-revealed to make the plot wholly believable for me at the end. I don't want to say more or I would reveal too much. I would be interested to hear what others think. What I think she did capture well was the oneness that some twins must experience and she did an excellent job portraying with great empathy someone with uncontrolled OCD.