The last book of the 7 foundation novels. It's about how Hari Seldon develops his plan and psychohistory. And how he has to deal with the power struggles of Galactic Politics and the Empire. In the process he loses everybody close to him, finally continuing almost alone, pushing the Seldon plan into action, to ease the suffering of humanity during the dark ages between the two Galactic Empires. The only person still helping him, is his adopted and gifted granddaughter.
The whole Foundation Series is simply awesome. 7 books in total, they are all worth it. And all the rest of Asimov is worth it too, especially the Robot Series.