Geronimo Stiltonn The Mona Mousa Code
 
The world's most famouse painting is hiding a big secret! An X-ray of the Mona Mousa reveals a strange riddle. Solving the clues takes Geronimo to the most dangerous parts of the city, but facing the hair-raising rollercoasters and vicious octopuses is all worth it for the amazing treasure at the end of the trail. Isn't it?

The series is perfect for both avid and reluctant readers aged 5-7 due to its expressive typeset, fun illustrations and humorous stories.