"Her Fearful Symmetry" by Audrey Niffenegger

Julia and Valentina are 20 year old twins who are joined at the hip. They inherit their aunt's apartment in London and her wealth, under the condition that they live in the apartment for one year. The girls move to London from America, and soon find that they are not alone and are living with their aunt's ghost. Also, the aunt's boyfriend is still around, along with an OCD'ed upstairs neighbour. I am classifying this as Sci-Fi because of the ghost factor. I liked this book a lot. The ghost thing isn't tacky and the book itself is fairly serious, but easily read. Lots of twisty turns at the end. This is by the author of "The Time Traveler's Wife".