Ace Books is the oldest active specialty publisher of science fiction and fantasy books (example pictured) and issued many of the best known science fiction writers of the 1950s and 1960s. The company was founded in New York City in 1952 by Aaron A. Wyn, and began as a genre publisher of mysteries and westerns. It soon branched out into other genres, publishing its first science fiction title in 1953; this was a successful innovation, and within a few years, such titles outnumbered both mysteries and westerns. Ace became known for the tête-bêche binding format used for many of its early books, although it did not originate the format. Most of the early titles were published in this "Ace Double" format, and Ace continued to issue books in varied genres, bound tête-bêche, until 1973. These have proved attractive to book collectors, and some rare titles in mint condition command prices up to $1,000. It was one of the leading science fiction publishers for its first ten years, but its fortunes began to decline after the death of owner A. A. Wyn in 1967. Two prominent editors, Donald A. Wollheim and Terry Carr, left in 1971, and in 1972 Ace was sold to Grosset & Dunlap. It is now an imprint of Penguin Group (USA).