The first in a trilogy, this novel is more focused on plot than on individual characters, and more focused on theme than on much of anything else. Asimov essentially sets out to tell the history of a galactic society, and this history has smackings of the history of Western civilization. I'm reminded a lot of the history of the Roman Empire. In terms of novels, I'm reminded of multigenerational novels, like Naguib Mahfouz's The Harafish.
We begin at a time when a single empire dominates the galaxy. Unfortunately, its power is waning. But historical forces, at least from the perspective of the novel, are predictable. And one psychohistorian, as such people are called, has figured out, via math and science, what the future holds. Follow his advice, and when the empire falls, it will reestablish itself in a thousand years; don't follow it, and the empire won't return for thirty thousand years. Luckily, he's smart enough to have been able also to predict how the rulers of the empire will react. They banish him to the outskirts of the empire, but they allow him to create an encyclopedia, which will store all of society's knowledge (the idea of such a book seems, in a way, rather antiquated now, in our Internet age).
True to form, the Foundation, as it is called, does retain scientific knowledge. But it does so without much in the way of control over the planet where it is centered. Meanwhile, the edges of the empire have collapsed, and in its place, are now a set of warring planets. The Foundation remains, however, through clever politics, playing one planet against another--and also by forging a religion. The religion gives it power in a soft sense but not a hard sense (think Catholicism of the Middle Ages). The priests control the masses, and the ruling class dare not stray too far from what the heads of the religion (i.e., the Foundation) wants.
As time moves forward, however, religion's influence begins to wane in favor of traders (capitalism, mercantilism, etc.). Now it is these men who play one planet against another, introducing technologies in order to further the Foundation's control.
A book of ideas more than characters, the piece focuses on three main crises. One doesn't end up caring much about any of the people involved, but as a book of ideas, it is fairly interesting.