More than 1.6m Geronimo Stilton books have been sold in Italy, 1.1m behind the four Harry Potter books published so far.
Like Harry in this country, Geronimo has inspired many Italian children to read more often, and the green-suited mouse is also set to leap from the book to the screen in a cartoon.
Ready to take on the world
No one knows who really writes the books with Geronimo's name on the cover, but they've been busy over the last two years, because 34 books about the mouse have been published!
And having taken Italy by storm, Geronimo is ready to take on the rest of the world, with his books ready to go on sale in Brazil, Belgium, France, Japan, Turkey, Lithuania, Latvia, Portugal and Spain.