Shannon Messenger is an American author. She is known for writing the middle-grade series Keeper of the Lost Cities, which was a New York Times bestseller; Unlocked, book 8.5 in the series, reached number 8 on USA Today's list in 2020. She also wrote the young-adult Sky Fall series. Her books have been published by Simon & Schuster. == Personal life == Shannon Messenger was born in Southern California. When she was young, she moved to San Diego and went to elementary school there. She graduat…