The 39 clues Is Scholastic's groundbreaking new series, spanning 10 adrenaline-charged books, 355 trading cards, and an online game where readers play a part in the story. The 39 clues books set the story, and the cards,...The 39 clues Is Scholastic's groundbreaking new series, spanning 10 adrenaline-charged books, 355 trading cards, and an online game where readers play a part in the story. The 39 clues books set the story, and the cards, website and game allow kids to participate in it.