What is the theme in The Unquiet Earth: A Novel by Denise Giardina?

The main theme of The Unquiet Earth by Denise Giardina is love. But there are several sub-categories of this theme. One theme that runs throughout the story which relates the lives of several generations of a family in a coal mining community in Appalachia is that of unrequited love and how it impacts one's life. From the time Dillon is a young teenager to the end of his life, he loves Rachel Honaker.