Her Fearful Symmetry
Julia and Valentina are twins, just like their mother Edie and her sister Elspeth were, except that Edie had a falling out that has separated them for 21 years. When Elspeth dies and leaves her London flat to Julia and Valentina with the instructions that they must live there a year before they can sell the flat, and that their parents may never step foot in it. Julia and Valentina move to London and realize they are more different then they thought, with the help of a ghost and their neighbors.
Having been uninterested in the Time Travelers Wife, I was surprised to find myself drawn to Her Fearful Symmetry. Niffenegger makes the existence of ghosts acceptable, and her characters real. The premise is just far fetched enough to keep readers interested, and the writing style such that you'll be reading for hours without realizing it. The twist at the end is regrettable, weird, and a little sad. Definitely worth a read.