The Princess Diaries, a young adult novel and the first in the series of the same name, follows the story of ninth-grader Mia Thermopolis, who discovers that her estranged father is actually a prince, making her a princess. Mia, with her gangly limbs and busy hair, begins taking etiquette lessons with her grandmother in order to learn how to act like royalty. At the same time, Mia must deal with other issues, like fighting with her best friend Lilly and her mother dating one of her teachers.
Mia Thermopolis is an average urban ninth grader. She lives in Greenwich Village with her single, liberal mother, who is a semi-famous painter, but Mia puts on her Doc Martens one at a time, and the most exciting things she ever dreams about are kissing senior Josh Richter ("six feet of hotness") and passing Algebra.
Mia's father comes to town and drops a major bomb: he's not just a European politician as he's always led her to believe, but actually the prince of a small country. And Mia, his only heir, is now considered the crown princess of Genovia. She doesn't even know how to begin to cope: "I am so NOT a princess.... You never saw anyone who looked less like a princess than I do. I mean, I have really bad hair... and... a really big mouth and no breasts and feet that look like skis."
Mia's troubles are worsened: her mother has started dating her algebra teacher (Frank Gianini), the paparazzi are showing up at school, and she has a fight with her best friend Lilly. After this they don't talk for a while and become distant from each other. Mia goes to her Grandmère's Plaza Hotel room in order to begin princess training, where she starts to develop into a great princess. Throughout the story Mia also makes another friend named Tina, who is shunned because of her overprotective father, who makes her have a bodyguard.