Each book, published by Ace, contains two "back to back" titles as shown in pics. Ace # / Title (author) 1) Ace D-407: The Planet Killers (Silverberg) and We Claim These Stars (Anderson) 2) Ace F-265: The Houses of Iszm (Vance) and Son of the Tree (Vance) 3) Ace 15697: Dr. Futurity (Dick) and The Unteleported Man (Dick) 4) Ace H-103: Code Duello (Reynolds) and The Age of Ruin (Faucette) 5) Ace G-723: Star Hunter (Norton) and Voodoo Planet (Norton) 6) Ace 37062: Gateway to Never (Chandler) and The Inheritors (Chandler) 7) Ace 68310: Project Jove (Glasby) and The Hunters of Jundagai (Bulmer) Conditions are mixed, mostly good. Notes by number above. 1) general wear, binding feels loose at cover 2) wrinkle on iszm side 3) Creased spine, writing on Futurity cover 4) tear at top spine, creased spine, sticker on Code front, writing on Ruin front 5) Like New 6) Large chip (and growing) on Gateway front, creased spine 7) creased spine, writing and wrinkle on Jove front All have tanned pages