"The Princess Diaries" is a young adult novel by Meg Cabot that follows the life of Mia Thermopolis, a teenager who discovers she is the heir to the throne of the fictional European country of Genovia. As she navigates the challenges of adolescence, Mia must also learn how to embrace her royal identity while dealing with the pressures of high school. The story explores themes of self-acceptance, friendship, and the importance of family. Mia's journey is filled with humorous and relatable moments as she transforms from an awkward girl into a confident young woman ready to take on her royal responsibilities.