The book I vaguely remember had something to do with a child or maybe siblings going to spend the summer with an elderly aunt (I think) who was living on a lake where most of the houses were abandoned. It had once been a vibrant summer community ca. 1900 (I think), but was now mostly deserted sans aunt’s household. There may or may not have been a mystery component to it. I think I read it around 4th grade maybe ca. 1977?