The Grownup  (Paperback, Gillian Flynn)

"A young woman is making a living faking it as a cut-price psychic (with some illegal soft-core sex work on the side). She makes a decent wage mostly by telling people what they want to hear. But then she meets Susan Burke. Susan moved to the city one year ago with her husband and 15-year-old stepson Miles. They live in a Victorian house called Carterhook Manor. Susan has become convinced that some malevolent spirit is inhabiting their home. The young woman doesn't believe in exorcism or the supernatural. However when she enters the house for the first time, she begins to feel it too, as if the very house is watching her, waiting, biding its time . . ."