New York, Doubleday, 1956. First edition, first impression. Hardback. A very good copy. First published in Astounding, this novel gave Heinlein his first Hugo award. Spine tips chipped and worn, with a bit of loss to the lower tip. Lengthy tear of around 50mm to the spine, and a shorter one to the top edge. A nice copy overall. Illustrations by Mel Hunter [9595, Hyraxia Books].