Don't Judge a Girl by Her Cover is a 2009 young adult novel written by Ally Carter. It is the sequel to Cross My Heart and Hope to Spy and the third book in the Gallagher Girls series. It was published on June 9, 2009. The cover was released on March 19, 2009. As of February 28, 2009, author Ally Carter posted mini-excerpts of the book on her blog, with the promise that while they would be in the book, they might be misleading. The book spent three weeks, from June 19, 2009 to July 3, 2009 on the Children's Books version of New York Times Best Seller list, debuting at #6.