Mr. Asimov has failed to integrate the necessary background into the current action in a way that can make sense to a new reader (as he did so deftly in ''Foundation's Edge'' and ''Robots and Empire''). Worse, he is too busy referring the reader to positions staked out in the earlier books to create fresh sources of dramatic tension. In his younger days, when he chronicled the decline and fall of the Galactic Empire through plots borrowed from Roman history, he tagged his narratives with playful quotations from the ''Encyclopedia Galactica.'' Now he seems to be treating his own corpus of work as the stuff of history. His characters are so conscious of their awesome responsibilities that they lack spontaneity. As eager as I am to know what Mr. Asimov has in store for the galaxy, I hope that he continues this project out of real conviction and not merely from habit or a sense of obligation. I would prefer a few loose ends to a series of backward-looking sequels.

Does the Foundation series really end here? Near the end of the novel, we are given a clue to what may be yet to come. An idiosyncrasy of Asimov's Foundation/Robot universe has always been that mankind has expanded into an empty and almost lifeless galaxy with no intelligent aliens, a galaxy where men and the robots are the only intelligent life forms. Now we receive a hint that there may be intelligent alien life in other galaxies and that mankind and these aliens may be destined to meet. Isaac Asimov is an amazingly prolific writer, and he has been well rewarded for his recent efforts. I would not want to bet that "Foundation and Earth" is really the conclusion of the Foundation series.