AFTERWORD BY THE AUTHOR
This book while self-contained, is a continuation of The Foundation Trilogy, which is made up of three books: Foundation, Foundation and Empire, and Second 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 in The Stars, Like Dust and The Currents of Space take place in the years when Trantor was expanding toward Empire, while the events in Pebble in the Sky take place when the First Galactic Empire was at the height of its power. In Pebble, 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 are to be found in The Complete Robot, while the two novels, The Caves of Steel and The Naked Sun, describe the robotic period of the colonization of the Galaxy.
If you wish an account of the Eternals and the way in which they adjusted human history, you will find it (not entirely consistent with the references in this new book) in The End of Eternity.
All the books mentioned existed as Doubleday hardcovers, to begin with. The Foundation Trilogy and The Complete Robot are still in print in hardcover. Of the others, Pebble in the Sky and The End of Eternity are included in the omnibus volume The Far Ends of Time and Earth, while The Stars, Like Dust and The Currents of Space are in the omnibus volume Prisoners of the Stars. Both omnibus volumes are in print in hardcover. As for The Caves of Steel and The Naked Sun, they are included in the omnibus volume The Robot Novels, still available from the Science Fiction Book Club. And all are in print in softcover editions, of course.