Books 30-50 from the Geronimo Stilton Series. 31 The Mysterious Cheese Thief 32 Valley of the Giant Skeletons 33 Geronimo and the Gold Medal Mystery 34 Geronimo Stilton, Secret Agent 35 A Very Merry Christmas 36 Geronimo's Valentine 37 The Race Across America 38 A Fabumouse School Adventure 39 Singing Sensation 40 The Karate Mouse 41 Mighty Mount Kilimanjaro 42 The Peculiar Pumpkin Thief 43 I'm Not a Supermouse! 44 The Giant Diamond Robbery 45 Save the White Whale! 46 The Haunted Castle 47 Run for the Hills, Geronimo! 48 The Mystery in Venice 49 The Way of the Samurai 50 This Hotel Is Haunted!