The story of how Hari Seldon's Psychohistory is used to try to cushion the fall of the galactic empire. Actually a collection of short stories, I enjoyed the intersection of politics and religion.

Some of the psychological aspects are interesting, particularly the Heisenburg-like repercussions of psychohistory (if people know you've made a certain predition about their behavior, that can AFFECT their behavior and change the outcome).