One False Note is the second book in The 39 Clues series. It is written by Gordon Korman, and was published by Scholastic on December 2, 2008. Following the events of The Maze of Bones, the protagonists Amy and Dan Cahill learn about Mozart and travel to Vienna, Austria to search for the second clue in the 39 Clues competition. One False Note entered the Children's Books New York Times Best Seller list at number one on December 21, 2008 and stayed on the list for children's chapter books for 12 weeks.

Gordon Korman is a Canadian author of children's and young adult fiction books. Korman's books have sold more than 30 million copies worldwide over a career spanning four decades and have appeared at number one on The New York Times Best Seller list.