In 1936, tucked deep into the woods of Troublesome Creek, KY, lives blue-skinned 19-year-old Cussy Carter, the last living female of the rare Blue People ancestry. The lonely young Appalachian woman joins the historical Pack Horse Library Project of Kentucky and becomes a librarian, riding across slippery creek beds and up treacherous mountains on her faithful mule to deliver books and other reading material to the impoverished hill people of Eastern Kentucky. Along her dangerous route, Cussy, known to the mountain folk as Bluet, confronts those suspicious of her damselfly-blue skin and the government's new book program. She befriends hardscrabble and complex fellow Kentuckians, and is fiercely determined to bring comfort and joy, instill literacy, and give to those who have nothing, a bookly respite, a fleeting retreat to faraway lands.