Brackett, Leigh. The Nemesis From Terra.
Silverberg, Robert. Collision Course.
New York: published by Ace Books, Inc. 1961.
Small octavo, pictorial wrappers. Ace double #F-123. First printing and first publication of The Nemesis From Terra. Wear to covers, wear to edges and corners; wear to spine corners, slight cant to spine, light discoloration; age tanned end pages; browning to interior covers edges, light age tanned text pages; Very Good.