Julia by Peter Straub
Trade paperback format.
Julia’s first purchase upon leaving her husband is a large, old-fashioned house in Kensington, where she plans to live by herself, well away from her soon-to-be-ex and the home where their young daughter died. She feels a peculiar affinity for the house right away, a feeling that deepens with each glimpse of a mysterious little girl–blond, like her daughter–in the neighborhood, and even in her dreams
But the little girl and the big house have an inexplicable aura of evil. And Julia quickly discovers that escaping her past is not as simple as turning a key.