YMMV: Old Man's War
- Author's Saving Throw: In the afterward for Zoe's Tale, Scalzi admits that a major motivation to telling a parallel story was to make Zoe returning with exactly what the Roanokers needed feel like less of a Deus ex Machina. It also let him give some closure to the werewolves.
- Old Man's War, as an homage to Starship Troopers, was naturally committed to a Crapsack World view of the universe in which humanity's only options were extinction or perpetual warfare against any race capable of occupying Earth-like worlds. (Though even in that book, the Straw Character 'has a point' and the Consu clearly aren't following the CDF's script.) The Ghost Brigades and The Last Colony invert this bleak worldview entirely, suggesting that many alien races can come to long-term peaceable agreements about territory - which leaves the CDF an example of Humans Are the Real Monsters.
- Many aspects of Old Man's War can lead to some rather nasty Fridge Horror regarding just how certain aspects of the Colonial Defense Forces work, in particular the use of Brain Uploading to extend life by transferring a human's mind into a Blank Slate clone, or the use of enhanced Blank Slate clones sans personality to create what are essentially Child Soldiers. The sequel, Ghost Brigades is largely an exploration of much of this Fridge Horror to show that many characters In-Universe have similar concerns both about the Super Soldier program and the state of humanity's foreign policy.