Shannon Messenger is an American author renowned for her captivating middle-grade series, Keeper of the Lost Cities, which earned a spot on the New York Times bestseller list. Notably, Unlocked, book 8.5 in the series, achieved the number 8 position on USA Today's list in 2020. She is also the creative mind behind the young-adult series, Sky Fall. Her works are published by Simon & Schuster.