"Succubus Blues" is a fantasy novel by Lisa Shearin that follows the story of Mackenzie "Mac" Santos, a young woman who works as a private investigator. She discovers that she is a succubus, a supernatural being that feeds on the life force of others, which complicates her life and relationships. As Mac navigates her new identity, she encounters various supernatural creatures and challenges. The novel blends elements of urban fantasy and mystery, showcasing Mac's struggle to balance her human emotions with her supernatural instincts while solving a series of intriguing cases.