So how will those clues work?

“The 39 Clues” is publishing on an aggressive timetable, with plans to release one book every two to three months. Rick Riordan wrote the first book (due out tomorrow!) and outlined the next nine novels, which will be written by other authors.
Scholastic has started to use its marketing power, tied to a Web-based game (www.the39clues.com) and collectors’ cards. The publisher, which thrived on the enormous success of the Harry Potter novels, is now facing the reality that many children are now as engrossed in the Internet and video games as they are in books.
“The idea is that every aspect will add to the storytelling in its own way,” said David Levithan, an executive editorial director for multimedia publishing at Scholastic. “The Web or card experience is not at all going to replicate the book experience, nor is the book experience going to replicate the Web.”
Levithan and three other Scholastic editors wanted to make sure that the books would complement the Internet game. Each of the 10 books would reveal only one clue per title, leaving gamers to find the other 29 online; another was that the series take place in a number of locales around the world.