Day of the Triffids (1951) by John Wyndham
This is your regular post-apocalyptic novel infused with heavy doses of Cold War paranoia. As you can see it was written in 1951 when nuclear bombs were on everyone's minds. However, Wyndham actually avoids the nuclear trope fairly well and instead focuses on satellite missiles which must have been a pretty new, if not still theoretical, technology at the time of writing.
The narrator finds himself in a world where most everyone has gone blind. Through a convenient accident he is not blind and he soon finds others who are not as well. Despite this happening overnight society has suddenly collapsed with only rare semblances of it's former self. Thus we get a good glimpse of survival ethics and psychology as the narrator bounces around London trying not to get sick or murdered. To add to the fun there are also the triffids. These strange plants appeared out of nowhere and slowly began exhibiting signs of intelligence. Humans being humans, they just ignored the triffids unless they caused a direct problem. Now that most people are blind the triffids decide to take over the world, something that seems fairly easy for them.
Despite the fact that it is supposedly their "day" not much time is spent examining the menace of the triffids. It almost seems an afterthought really. The climax of the book comes and goes without resolution of the triffid problem. In fact, the characters place much of the blame for the current situation on the arms race and the selfishness and insecurity of nations. A very biting book at the time, I am sure.
For someone quite removed from the Cold War mentality this conclusion only serves to amplify the convenience of the triffid problem. Okay, so if they aren't an alien species bent on world domination and had nothing to do with causing the blindness pandemic then where did they come from? What's their motivation? Why did they suddenly start breaking loose and rampaging about London the very day after people lost their sight? Too many questions left unanswered for my liking, but I probably would've overlooked those and been affected more by the message had I read it when it was first published.