Geronimo Stilton , is a best-selling book series written by Geronimo Stilton. In the series, Geronimo Stilton is a fictional character, an Italian speaking mouse who lives in New Mouse City on The Island of Mice. A best-selling author, he works as a journalist for the fictional newspaper The Rodent's Gazette . He has a younger sister named Thea Stilton, a cousin named Trap Stilton, and favorite 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. The books are written as though they are autobiographical adventure stories. Geronimo investigates the rumors of a secret hidden in Mouse City's most famous painting, the Mona Mousa, and follows a trail of clues which lead below the streets of New Mouse City.