The Ghost Sitter (Electronic book text)

Charlotte is looking forward to spending the summer in her new home-she has her own bedroom, a nearby pool, a friendly neighbor, and there's a big block party coming up. Then her little brother suddenly starts asking for his new friend, ""Susie."" Is someone else playing with him? Someone only he can see? Soon Charlotte realizes that her all-too-normal house is haunted-by the ghost of a girl who doesn't realize that she's dead. . . .
""Has several strong appeals: new best friends solving a mystery together, a just-scary-enough ghost girl, and a deathless bond between sisters that provides the book with its resoundingly satisfying conclusion.""("The Horn Book")