The Gray Man Series is a collection of action-thriller novels written by author Mark Greaney. The series follows the character Court Gentry, a former CIA operative turned assassin, known as "The Gray Man" due to his ability to blend into any environment and evade detection. The books are known for their fast-paced plots, intricate espionage, and intense action sequences. The first novel, titled The Gray Man, was published in 2009 and has since spawned several sequels. The series has gained a loyal following and has been praised for its realistic portrayal of covert operations and military tactics. In 2022, the series was adapted into a film starring Ryan Gosling, further increasing its popularity.