If you were captivated by John Perry's journey through training and interstellar war, you'll be drawn to William Mandella's relentless fight against the alien Taurans. The Forever War shares that clear, driving sense of purpose—the survival and success of soldiers in a brutal, endless conflict. The mission-focused narrative keeps the stakes high and the tension sharp, just as you enjoyed in Old Man's War.

Loved the snappy, sardonic tone and John Perry's wry observations? You'll find plenty to laugh about in Redshirts, where a group of starship crew members realize something is seriously off with the way their missions go. The razor-sharp dialogue, meta-humor, and genre-savvy jokes make this a perfect follow-up for anyone who appreciates Scalzi's comedic touch in Old Man's War.

If John Perry's journey from a widowed retiree to a battle-hardened soldier fascinated you, you'll be equally intrigued by Takeshi Kovacs—a man forced to adapt and evolve as his consciousness is transferred between bodies. Altered Carbon offers gritty, transformative arcs as characters grapple with identity, morality, and survival, echoing the compelling growth you loved in Old Man's War.

If you enjoyed the expansive universe and high-stakes space battles of Old Man's War, you'll be thrilled by the sweeping scope of Leviathan Wakes. With complex interplanetary politics, alien mysteries, and a cast of characters navigating crises across the solar system, this book delivers the same thrilling sense of adventure and scale.

If you appreciated how Old Man's War wove advanced technology and plausible science into its story—like the BrainPal and genetically engineered bodies—you'll love the meticulous, science-driven survival story of Mark Watney on Mars. The Martian delivers hard science with wit and tension, making every challenge and solution feel real and rewarding.