This is an intriguing historical fiction about a woman who is a pack horse librarian in the 1930s. The story follows Cussy Mary as she travels the mountain to share books with her patrons. It is a heartbreaking story to see how Cussy Mary is treated due to her blue skin which is a hereditary birth defect with her blood and how her father is treated as a mine worker in a time when mine workers had no rights. They had to live on the outskirts of town and away from people due to prejudices and segregation laws. People actually believed it was contagious. The medical aspects were interesting. I liked that the author used actual medical facts even though she did adjust the time period to make it fit the story. The facts at the end of the book let the reader know which is fact and which is fiction in the story.