Man, I almost got turned off the whole genre because so many apocalypse books just feel like video game logic with zombies slapped on. What really got me back into it was 'The Road' by Cormac McCarthy. It doesn’t bother with explaining the 'why' of the disaster, which is the point. The realism is in the sheer, grinding weight of survival—scrounging for a single can of food, the constant cold, the terrifying silence. It’s less about the world ending and more about what’s left of a person after it does. That book sits with you, heavy and quiet, long after you finish.
For a different flavor, Emily St. John Mandel’s 'Station Eleven' is fascinating. The realism there is in the aftermath, the way society rebuilds around art and memory instead of just bullets and bunkers. It feels plausible because it focuses on the connections people try to make, not just the monsters they have to fight. The Flu itself is almost a backdrop to the real story of what we carry forward.