When he begins receiving packages containing useless things he did not order, Geronimo Stilton discovers that someone on the Internet has stolen his identity, a dilemma that compels him to enlist the help of computer expert Professor Margo Bitmouse, who helps Geronimo track down the hacker.

Geronimo Stilton's ancient ancestor Geronimo Stiltonoot is back in another prehistoric adventure. Geronimo Stiltonoot and his family are off to find a cure for Grandma Ratrock's aches and pains. She's heard that a remedy hides in a legendary valley, and Geronimo isn't even sure it exists. Little does he know that getting there will be an adventure among geysers, volcanoes, and rivers of molten lava.

Geronimo Stiltonoot and his family save a young dinosaur from the river. The dinosaur and Benjamin quickly become good friends, but the dino turns out to have a tremendous talent for mischief. Can Geronimo get him back to his herd before he causes a megalithic disaster?

Determined to earn a mouseking helmet, Geronimo Stiltonord undergoes special training conducted by Miceking chief Sven the Shouter.

Geronimo Stiltonix takes MouseStar 1's broken computer to a distant planet to be repaired by a brilliant inventor, but pirate spacecats attack and steal the device, and the spacemice must retrieve it before the machine can be turned against them.

All the mammoths have fled Old Mouse City! It's a total cat-astrophe! Not only because mammoths are valuable allies of the cavemice, but also because without them, the cavemice can't make mammoth milkshakes, their delicious national drink. Geronimo Stiltonoot must embark on a daring journey to find the mammoths...and avoid going extinct before he gets back!

Drawn once again into the Kingdom of Fantasy, Geronimo discovers that the Land of Books is being threatened by a wave of grayness spreading from the Kingdom of Swamp Valley rotting books and turning all the characters gray, sad and worried--and it will be up to Geronimo, Winglet (daughter of Blossom and newly crowned empress), and the intrepid characters from fiction who join them along the way, to locate the source of this new evil and put a stop...

When Geronimo Stilton and his friends time travel to three different centuries seeking artifacts missing from the mouseum, they meet Alexander the Great, Queen Cleopatra, Francis Drake, and Mozart.