Having recently discovered she is the sole heir to the throne of a tiny European principality, fourteen-year-old Manhattan resident Mia writes in her journal about her attempts to cope with this news, as well as with more typical teenage concerns.

Princess Mia is introduced to her Genovian subjects, and more importantly, she goes out on a date.

In a series of humorous diary entries, high school freshman (and Genovian Princess) Mia tries to get her reluctant boyfriend to take her to the prom.

In a series of diary entries, Princess Mia describes celebrating Christmas with her friends in Genovia.

During the days before her sixteenth birthday, Mia records in her diary her fear that her grandmother and friends may be planning to throw an extravagant Sweet Sixteen party.

Princess Mia's junior year in high school begins with a difficult course load, a crazy student council race, Grandmere's search for temporary lodging, and learning that her boyfriend is moving to Japan for a year, partly because she will not sleep with him.

Although she has recently completed a 400-page romance novel, Princess Mia, in her last month of high school, has yet to pick a college, find a prom dress, or decide if her boyfriend J. P. is really The One.

Princess Mia's friends and assistants examine the style, accomplishments, and other characteristics of real and fictional princesses, as Mia gleans from each a "random act of princess" for self-improvement.