Join the Thea Sisters as they try to solve the mystery of who wrote a love letter on campus. Who has a secret admirer?

Geronimo Stilton is a best-selling children's book series published by Edizioni Piemme of Milan, Italy, since 2000. Scholastic Corporationhas published the English version of the series since February 2004. Although the series credits its title character as the author, the idea was originally thought of by Elisabetta Dami. On older novels, the copyright is issued to a pseudonym "Geronimo Stilton"; this was changed on newer books. The books are intended for readers in the 6–12-year-old age range.