The 39 Clues
The 39 Clues is a series of ten adventure books written by different authors including Rick Riordan, Gordon Korman etc.. In the series, the two main characters, Dan and Amy Cahill's grandmother. In her will, she says each person can get one million dollars or search for clues around the world and become super powerful. There are also online and card games. in book ten it states that all who pass through the gauntlet will get double the amount they turned down.