Meg Cabot's 'Princess Diaries' series will include two more installments

Cabot will release a novel for adults centering on the 'Princess' protagonist, Mia, and a book for younger readers with Mia's half-sister as the main character.

Author Meg Cabot has carried the adventures of teenager Mia Thermopolis – a New Yorker who discovers she’s actually the princess of a small European country – through 10 books as well as shorter titles. Mia’s adventures have also been adapted into two films.

Now Cabot says she’s returning to the world of Mia with two books, one aimed at younger readers and another that will center on Mia as an adult. The one for middle-grade fans will focus on a girl named Olivia Grace who finds out she is Mia’s half-sister and so also a princess. The book will include illustrations and will be published by Feiwel and Friends in the summer of 2015. The book will be the first in a planned series titled “From the Notebooks of a Middle School Princess,” according to Cabot.

Meanwhile, Mia herself will return in a novel for adults titled “Royal Wedding,” which is scheduled for release that summer. MIa’s engaged to her longtime boyfriend Michael when the press discovers the existence of Olivia. A plotter uses the uproar to try to take her father, the ruler of Genovia, off the throne.

The story of Mia was adapted into two films, the 2001 movie “The Princess Diaries” and 2004’s “The Princess Diaries 2: Royal Engagement.”

Cabot is the other of multiple other series for middle-grade readers, young adults, and adults, including the “Allie Finkle’s Rules for Girls” series and the Heather Wells mystery series.