From the blurb:
"Imagine living on a planet with six suns that never experiences Darkness. Imagine never having seen the Stars. Then, one by one your suns start to set, gradually leading you into Darkness for the first time ever. Image the terror of such a Nightfall.
Scientists on the planet Kalgash discover that an eclipse - an event that occurs only every 2049 years - is imminent, and that a society unfamiliar with Darkness will be plunged into madness and chaos. They realize that their civilization will end, for the people of Kalgash have a proven fear of Darkness, but they are unable to predict the insanity and destruction that will accompany the awesome splendor of Nightfall."
Originally published in 1970, this book has a pulp feel to it. This story explores the events before, during and after a total eclipse and resulting complete darkness on a planet with six suns and perpetual light. The doomsday/apocalypse concept is interesting but the execution falls a bit flat - the characters are a bit two dimensional and some events and their timing are just too convenient. However, the book is still enjoyable and would make a nice addition to the shelf of an apocalypse fan.