John Scalzi didn't take the traditional route to becoming a best-selling author. In fact, he was publishing a large portion of his fiction online for free when a literary agent discovered him and offered representation. His first major hit, Old Man's War became an unusual classic in the sub-genre of military science fiction. Set in a future where Earth has many far-flung colonies in need of protection, the novel turns the traditional "new recruits" army narrative on its head by having the troops be composed almost entirely of senior citizens and the very elderly. There's a catch, of course! The novel is by turns quite funny and sober, but maintains its inventiveness throughout. If you enjoy the book, Scalzi has also expanded the story with additional novels.