Old Guns Books in Order

Old Guns takes a fun military sci-fi premise and plays it straight enough to work: when humanity needs experts for a new alien crisis, the people who get called back are not shiny young heroes but two battered Marines who already survived first contact. Frank Cage and Martin Kelvin are older, rougher, and nowhere near retirement in spirit, even if their bodies would prefer otherwise.

That contrast is the whole charm.

The series pairs veteran-soldier grit with big alien-threat stakes. Frank and Martin are the kind of protagonists who know too much, trust too little, and complain the whole way to the battlefield. Around them the story builds a larger war involving the Hollow, later the Halcerite Empire, young recruits who have never seen real combat, and the sort of military bureaucracy that never quite understands the people it needs most.

It is funny in places, but not lightweight.

The books still run on combat drops, buried facilities, disappearing ships, weird alien biology, and missions where experience matters more than fresh theory. The prequel novella The Gauntlet reaches back to first contact, while later entries widen the war and force Frank and Martin to deal with enemies, defectors, and a galaxy that keeps getting messier. If you like military science fiction with older leads, sharp banter, and a lot of stomping through danger, Old Guns is easy to pick up.