Scholastic’s multimedia The 39 Clues series continued to grow this week, with the second book, One False Note by Gordon Korman, going on sale in the U.S., U.K., Australia, New Zealand and Canada. The first book was The Maze of Bones by Rick Riordan. One million copies of that title are now in print worldwide, along with an additional 500,000 trading card packs. One False Note landed with a 500,000-copy first printing.

In advance of the publication of One False Note, children around the world submitted thousands of questions for a webcast held Monday, during which actress/comedian Whoopi Goldberg interviewed Korman. (Click here to watch.) Korman fielded questions from readers, and author Peter Lerangis appeared with Goldberg and Korman during the webcast. Lerangis wrote The Sword Thief, the third installment in the 39 Clues series.

Scholastic also announced several new interactive features launching on the 39 Clues Web site. Arena 39 allows registered sitegoers to hone their skills with a selection of games and challenges. And instructions and downloadable materials for an offline card game, The 39 Clues: Double-Cross, which makes use of the 39 Clues collectible cards, are now available.

In the run-up to Christmas, Scholastic will support the series with TV ads in five markets, and the publisher has also created a teacher’s guide, available on Scholastic’s Web site. Additionally, three prize-winners in the contest portion of the program will be revealed in January; players from all 50 states and 100 countries are competing in the game.