Imagine time travel was possible. Would changes in the past affect the present? Most books assume that is the case. However this book assumes that the controlers of time travel are not affected by changes to their history. They use this to constantly prevent the errors of history. What sort of errors? War, they can prevent that from happening. Famine, by studying the factors that affected the events of the time a small change as insignificant as moving the position of a jar of beans would prevent a famine. Side effects? There were a few, millions would live, but billions would never get the chance to live. What would happen, in the past, and the future?
Yet another fascinating set of ideas presented by Isaac Asimov, well worth the time of reading, Rootie Rating 4 out of 5