Ace Double F-149 (40 cent cover price) 1962 paperback. Condition is VG+ or better: tight and almost square with flat spine (one end is square, other end has slight tilt - this is tight enough that it may be unread?) Very faint lines near spine and a couple of 1" finger-creases on each side. Age tanning is very mild and uniform - better than usual for a book almost 50 years old. There is part of a bookstore stamp on one of the top page-blocks; no other marks, stamps or writing.

Ace Double F-149, from 1962: Cosmic Checkmate, bound with King of the Fourth Planet.

Cosmic Checkmate by Charles V. DeVet & Katherine MacLean. Cover by Ed Valigursky; 96 pages. This is an expansion of "Second Game" from Astounding March 1958.
On Velda, The Game (a form of super-chess) was played from earliest childhood, and a vital aspect of their culture. Earth's alliance, The Ten Thousand Worlds, wanted peace with Velda. They won't talk, and obliterated the fleet bringing the initial peace overtures. So Earth sent in a ringer - Robert Lang - to try a different method of communicating. He played their Game in sets of two, with the motto: "I'll beat you the second game."

(Bound with) King of the Fourth Planet, by Robert Moore Williams. Cover by Ed Emshwiller; 128 pages. John Rolf had abandoned the corruption of Earth for a life of meditation on the many levels of Mars' mountain, ruled as tradition had it by a king with amazing powers. Here, Rolf perfected an invention to explore the human mind- and discovered a menace that threatened to destroy the ancient Martian culture. But agents of the Company are already present, wanting Rolf's secret. Will he defy Earth to save Mars?