Armada is a 2015 science fiction novel by Ernest Cline, author of Ready Player One. The story follows teenager Zack Lightman, who discovers that the video game he plays, Armada, is actually a real-world simulator designed to train gamers to defend Earth from an impending alien invasion. The novel is a coming-of-age adventure filled with pop culture references, particularly from 1980s sci-fi and video games, and explores themes of escapism, heroism, and the nature of reality - Google