I am, for some reason, working through the science fiction novels of Isasc Asimov. This one is made up of two stories, "The General" and "The Mule", that originally appeared in Astounding Science Fiction in 1945. They were first joined together in book form in 1951, and remain together to this day.
It's the middle volume of Asimov's "Foundation Trilogy" (which was later expanded into seven books, plus more by other authors). The Foundation was the project of psychohistorian Hari Seldon, who foresaw the imminent collapse of the Galactic Empire. The Foundation was established on Terminus, waaaaay out on the edge of the galaxy, to re-establish civilization and prosperity in a much shorter time than would otherwise be the case.
"The General" describes the final clash between the dying Empire and the surging Foundation. Things look grim for the Foundation, as an upstart military man, Bel Riose, decides to use the Empire's dwindling, but still vast, resources to rein them in. But he ultimately fails, and much of the story is devoted to showing how this was inevitable, and all in accord with Seldon's vision.
"The Mule" is the more interesting story; it involves the unforeseen wild card of a mutant with psychic powers, who single-handedly builds his own empire, and threatens the Foundation. Seldon's psychohistorical equations deal with mass societal trends, and are unequipped for a powerful single individual like the Mule.
This is a book I first read when very young, and by that time it was already a science fiction "classic". It's not as good as I remembered, but the Mule stuff is still pretty good.