"Nona the Ninth" is a fantasy novel by Tamsyn Muir, part of the Locked Tomb series. It follows the story of Nona, a young girl with a mysterious past, who possesses unique abilities. Set in a world filled with necromancy and complex relationships, the narrative explores themes of friendship, loyalty, and identity. The book features a blend of humor and dark elements, showcasing Nona's journey as she navigates her powers and the challenges of her environment. As she interacts with various characters, including Harrowhark Nonagesimus and Gideon Nav, the story delves into the intricacies of their connections and the larger conflicts at play.