Karen M. McManus is an American author known for her young adult mystery novels. She gained widespread recognition with her debut book, One of Us Is Lying, published in 2017, which became a bestseller and was adapted into a television series. Her writing often features suspenseful plots and complex characters, appealing to both teens and adults. In addition to her debut, McManus has written several other popular novels, including Two Can Keep a Secret and The Cousins. Her work typically explores themes of friendship, secrets, and the consequences of choices, making her a prominent figure in contemporary young adult literature.