Help me find a book but I cannot remember title or author
It is about a bookshop owner's daughter who is invited by a famous novelist to write a book for her. It is all very mysterious and she has to go to an old house, where the writer lives and is old and sick. It turns out to be her family history and involves strange twins and crazy parents. (The mother is dead, with her own strange past). The budding author has her own sad history - a twin who died at birth and a mother who could not love her. She has to research the old lady's story herself as she is only told bits of the story. It is not a very old book and has a ghostly element.
