Old Man's War

John Scalzi's debut is Old Man's War, military science fiction published in 2005; it made the Hugo shortlist for Best Novel in 2006, and the book opens the Old Man's War series, which has since taken the 2026 Hugo Award for Best Series and grown to several further novels. It was optioned for film in 2011.

John Perry turns seventy-five, buries his wife and joins the Colonial Defense Forces, which is what a lot of old people do, because the CDF only recruits people with decades of experience and nobody knows what its soldiers actually look like. The answer arrives after he leaves Earth and stops being seventy-five. What he signs up for is a ten-year term, and the terms of the enlistment mean he cannot go home again.

Humanity holds a handful of inhabited worlds in a galaxy that is crowded, and the colonies are won and kept by a force that fights for land, water and settlers with technology nobody back home is told about. Perry's first year in the CDF is boot camp, first contact and a long look at what the war is actually for. The book is written in his voice, so the military technology is explained only as far as he understands it.

The series continues in The Ghost Brigades, The Last Colony and several later books, including one told from the point of view of Perry's daughter. The first novel establishes the CDF, the colonial situation and Perry himself, and it can be read on its own.