THIS BOOK WHILE SELF-CONTAINED, IS A CONTINUATION OFThe Foundation Trilogy , which is made up of three books:Foundation ,Foundation and Empire , andSecond Foundation .
 
                In addition, there are other books I have written which, while not dealing with the Foundations directly, are set in what we might call “the Foundation universe.”
 
                Thus, the events inThe Stars, Like Dust andThe Currents of Space take place in the years when Trantor was expanding toward Empire, while the events inPebble in the Sky take place when the First Galactic Empire was at the height of its power. InPebble , Earth is central and some of the material in it is alluded to tangentially in this new book.
 
                In none of the earlier books of the Foundation universe were robots mentioned. In this new book, however, there are references to robots. In this connection, you may wish to read my robot stories. The short stories ar............