What is the book missing may about?

They have been a family for half of Summer's twelve years, and when her Aunt May dies, a little bit of Summer and her Uncle Ob dies too.... With homely detail, Rylant plunges readers into the middle of Summer's world, creating characters certain to live long in their memories. Her tightly woven plot wastes no Words.... [A] natural grace of language, an earthly sense of humor, and a well grounded sense of the spiritual.