Mama's Going to Buy You a Mockingbird — Jean Little

Jeremy is not having a good summer. His best friends have moved away, and he has to stay at the cottage with only his little sister and Aunt Margery. His parents have remained in the city so his father can have an operation.

When Jeremy finally sees him again, he finds out that his father has cancer and isn't going to get better. Suddenly, everything is different. Then Jeremy finds an unlikely friend in Tess, who knows what it's like to lose someone. As his friendship with her grows, through good times and bad, Jeremy discovers that his father has left him something that will live forever...