The Time of the Ghost

The Time of the Ghost is a supernatural English-language children's novel by Diana Wynne Jones, published by Macmillan in 1981. Set in the English countryside, it features a teenage ghost who is one of four sisters, and observes the family, unable to remember which one she is. She is from seven years in the future, in the aftermath of her "accident", so it is a kind of a time slip story, but she has no memories of those seven years.