Foundation is the series that brought the whole idea of adding a "Power Sources" topic to this web site. Technology is a major focus in Foundation and, since Asimov is trying to be as realistic as possible, he explains a lot about how this technology works.

The galaxy is falling into ruin. Disregard is being paid to any technological advances whatsoever. Some people have even gone back to using fossil fuels (heaven forbid!) even though the superior energy source of atomic power is available. One man, Hari Seldon, sees this decay and forms a new civilization out at the edges of the galaxy called The Foundation. They specialize in making technological advances and miniaturizing the technology already available (kind of like Silicon Valley). They use atomic energy as their main power source for everything and are able to fit powerful atomic generators in devices the size of a walnut.

In the last two books of the series the main characters travel around in a ship that makes use of antigravity and scoops energy from space itself. Pretty cool, huh?