The 39 Clues, the best-selling multimedia adventure series aimed at kids 8-12, was scheduled to end with the 10th and final book, Into the Gauntlet, to be released Aug. 31st. But publisher Scholastic is extending the franchise. Today, it’s announcing a guidebook to the series, about a family that has secretly dominated the world for the past 500 years. The 39 Clues: The Black Book of Buried Secrets will be released Oct. 26th. The introduction is by Rick Riordan, who wrote the first book, The Maze of Bones, in 2008 and outlined the arc of the rest of the series for nine other authors. DreamWorks has bought the movie rights.