Moon Island — Rosie Thomas

On the coast of Maine, five old houses are visited every summer by the same group of families. When 14-year-old May Duhane arrives for her summer vacation, following the death of her mother, and at the point of estrangement from her father and sister, she feels isolated and resentful. Then she discovers the eerie diary of Doone Bennison, a young girl who died in tragic circumstances on the island the year before.