The first five books have been published. The books are intended for readers in the 6–12-year-old age range.

In the series, the title character is a talking mouse who lives in New Mouse City on Mouse Island. A best-selling author, Geronimo Stilton works as a journalist and editor for the fictional newspaper The Rodent’s Gazette. 
 

He has a younger sister named Thea Stilton, a cousin named Trap Stilton, and a favourite little nephew, nine-year-old Benjamin Stilton. 

Geronimo is a nervous, mild-mannered mouse who would like nothing better than to live a quiet life, but he keeps getting involved in far-away adventures with Thea, Trap, and Benjamin, and sometimes Aunt Sweetfur. 

The books are written as though they are autobiographical adventure stories.

The series originated in Italy and has become the most popular children's book series in that country. The books have been translated into 40 languages.

There are also other media versions of the Geronimo Stilton books, including animated series, musical theatre and comics/graphic novels.