During the whole Foundation series, one man has always had his hand in the development of a galaxy. Merely hinted at in previous books, visited off and on for historical background - finally here delved into as deep as one can go - the demystified Hari Seldon. This follows about 40 years of his life, and traces his progress in the development of Psychohistory - the pseudo-mathematical science that would one day save the galaxy.

If you have read the Foundation series, either in it's entirety or just pieces, this is a must read. It also (if memory serves) is the last book Asimov wrote before his death - the final pages describing Hari Seldon's final moments of life mirroring his own. A truly beautiful read.