This is a great dystopian story and like all John Wyndham; so well written. This is my third favourite of John Wyndham novels. Its not that it does not make the grade, because it does. Its just that The Midwich Cuckoos and The Chrysalids were so fabulously out there. The Day of the Triffids is too, so my advise is to read all three. You'll not be disappointed in any of these sci/fi gems.
The Day of the Triffids gives us a chilling dystopian world were Triffid plants are being cultivated for their oil and so on. The plants are dangerous because they can move and have a lethal sting. Only specialists can farm them.
Then a meteor shower cripples the world population. Over night everyone who witnessed the comet display becomes blind by the following morning. Civilisation is at an end and nothing can function. Only a handful of people, who never saw the meteor display, can see. They are so few in number that they cannot do anything for the multi-millions of people who are blind.
The cultivated triffids brake free from the confines in the agriculture industry, which no longer functions. As said, the plants can move and have a sting. They can also consume dead flesh. The blind population are a feast awaiting triffid attention.
The world is turned upside down and the survivors with sight have their work cut out for them. Only the strong and ruthless can survive. The millions of blind are of little use.
Now you get the picture?