Everything seemed fine with the domesticated Triffids until the Earth passed through the tail of a comet, blinding much of the world's population. It was then the Triffids struck!
I love the proto-sf of the first half of the 20th century, when the lines between sf and horror were more blurred than they are now. Day of the Triffids is one of those books that many things that came later owe a debt to. The roots of the survival horror genre can be found within its pages, in my opinion. Many zombie flicks owe a debt of gratitude to this book. Heck, 28 Days Later lifted the beginning directly. Guy wakes up in hospital to find the whole world has changed while he was asleep. Sound familiar?
The Triffids themselves are a little ridiculous but still scary. A walking plant with a venomous sting is nothing to laugh at.