Each is hardcover with dust jacket. First title “Islands In The Sky” is 6x8-5/8” first edition with 212 pages with dust jacket and end paper art by Alex Schomburg. Front shows astronauts in outer space floating their space station. Inside covers have multi-scene image including robot destroying building with ray from his helmet as crowd flees. Published by John C. Winston Co. Philadelphia. Dust jacket has scattered lt. wear across top and bottom edges with clipped corners on inside flaps. Displays Fine. Endpapers of book have narrow tan streak along seam. Book o/w VF/Exc. “Sands Of Mars” title is 5-5/8x8.5” with 120 pages. First Gnome press edition in non-illustrated dust jacket. Dust jacket has lt. dust soil with tiny pieces missing at extreme top and bottom margin edges here and there including spine. Inside of spine has archival tape for support. Inside flaps have corner clips. Dust jacket Good. Book has tiny bit of wear at spine tips. VF/Exc. Nice early books by the famed author of 2001: A Space Odyssey.