Her Fearful Symmetry by Audrey Niffenegger

Just finished this book.  It is from the same author as Time Traveler's Wife.  It is a story about Twins among other things.  It immediately grips you and keeps you wanting to find out how the characters are connected.  In the middle, the story plateaued and took an odd turn.  Then the ending was somewhat surprising, but disturbing.  It's a good read.