Seventeen selections arranged in order of increasing controversiality represent Asimov's recent essays on astronomy, chemistry, biology, and other topics pertinent to the future of man
Used availability for Isaac Asimov's The Planet That Wasn't
Hardback Editions
September 1976 : USA Hardback

Title: The Planet That Wasn't
Author(s): Isaac Asimov
ISBN: 0-385-11687-X / 978-0-385-11687-9 (USA edition)
Publisher: Doubleday
Availability:
Amazon Amazon UK Amazon CA Paperback Editions
1977 : USA Mass Market Paperback

Title: The Planet That Wasn't (Discus, No.35709)
Author(s): Isaac Asimov
ISBN: 0-380-01813-6 / 978-0-380-01813-0 (USA edition)
Publisher: Avon Books
Availability:
Amazon Amazon UK Amazon CA July 1977 : UK Paperback

Title: Planet That Wasn't (Sphere science)
Author(s): Isaac Asimov
ISBN: 0-7221-1258-0 / 978-0-7221-1258-8 (UK edition)
Publisher: Sphere
Availability:
Amazon Amazon UK Amazon CA January 1977 : UK Mass Market Paperback

Title: The Planet That Wasn't
Author(s): Isaac Asimov
ISBN: 0-7221-1238-6 / 978-0-7221-1238-0 (UK edition)
Publisher: Discus
Availability:
Amazon Amazon UK 1977 : UK Paperback

Title: The Planet That Wasn't There
Author(s): Isaac Asimov
ISBN: 0-7221-1261-0 / 978-0-7221-1261-8 (UK edition)
Publisher: Sphere
Availability:
Amazon