People fear death (apparently just a tiny bit less than public speaking).
We don't know how to talk about it, especially to children, and we're afraid to bring it up for fear of making people sadder.
Yet children, especially, have questions, and this incredibly gentle and surprisingly light story is full of both comfort and vividly imagined answers.
The first one gives the book its title: A boy hears the voice of his sister calling him one day, a sister he's never met because she died befo.