After seeing a number of these "help me find this story" stacks, I thought I'd throw in my own.
As scifi book I read decades ago. A German translation of a US novel, I believe.
It's a post-apocalyptic novel about an enclave that is trying to survive with a planet going to hell. I believe the enclave was following along the "wise and prepared billionaire" trope, who collected The Best and hoarded resources to try and continue civilisation.
The format of the novel, though, is in the form of chapters that look back at crucial events that preceded the collapse. Of these I remember 3:
- Flesh-eating venomous worms that had been kept in check by fish, suddenly exploded on to land. Over-fishing had removed their predators, so they now regularly came on to land, billions of them and literally poisoned and ate everything along the coastal regions of the world
- Soviet Russia and the Communist bloc still existed. A fad of super-virtual reality (one of the first mentions of the concept I ever read, way back in the late 70s) swamps the planet and helps people zone out (think OASIS). Communist governments try to ban the technology which actually drives their people to revolt, which leads to such violent uprisings and civil war that it goes nuclear, devastating large parts of the planet.
- Food and health controls had become meaningless and companies were able to issue unbelievable crap that could actually kill you. One company made ready-to-eat meals that caused, literally, internal combustion. Intestinal build up of inflammatory and explosive gases that would ignite and kill a person or animal if it came into contact with a spark.
The story ended sadly: the narrator was on a mission or patrol, when he receives word that even the sanctuary/enclave had succumbed to yet another disaster.
It wasn't the best of scifi novels but it left a memory because some of it was eerily prescient.