Foundation

Worth re-reading for the concept of psychohistory, and the confidence that human nature, appropriately convened, will overcome crises. When I first read it, it didn't seem at all likely that large numbers of people could be persuaded to behave idiotically en masse. 

Blip is of the dust jacket of my copy, marked copyright Asimov 1951, but actually published by Doubleday in 1952. Also blipped when I was making pictures of the books on my shelves. All the others in this image were donated before we moved from California.

 Wikipedia article lists people and writings influenced by the series, including Douglas Adams; it also lists radio, film and TV series adaptions.