Ace Books was founded in 1953 by A. A. Wyn, and is the oldest continuously operating science fiction publisher in the United States. With Donald A. Wollheim as editor, it issued some of the most outstanding science fiction writers of the 1950s and 1960s, including Samuel R. Delany, Philip K. Dick, Ursula K. Le Guin, and Robert Silverberg. Ace was known for marketing innovations such as the Ace Doubles, which contained two short novels bound back to back, and for the critically acclaimed Ace Specials edited by Terry Carr. In 1972, Wollheim left the company, and it was later acquired by Grosset & Dunlap. Under Publisher Tom Doherty, Ace produced books in all genres, though science fiction remained a specialty. In 1982, Grosset & Dunlap was acquired by G. P. Putnam's Sons (later known as The Putnam Berkley Group), and Ace soon became Berkley's science fiction imprint. The combined backlists of Ace and Berkley made a powerful presence in the science fiction field, with Frank Herbert's bestselling Dune series, T. H. White's classic Arthurian novel The Once and Future King (basis for the musical Camelot), much of Robert A. Heinlein's adult fiction, including Stranger in a Strange Land, and the novels of William Gibson, including Neuromancer, which is credited with introducing the concept of cyberspace. More recent important authors include: Joe Haldeman, winner of the 1998 Hugo and Nebula awards for Forever Peace and the Nebula Award for Camouflage; Hugo Award-nominee Charles Stross and Alastair Reynolds, two in the current generation of British science fiction writers who specialize in the "new space opera"; National-bestselling science fiction author Jack McDevitt, whose novel have garnered more Nebula nominations than any other author in the genre; Charlaine Harris, whose Southern Vampireseries grew out of mass market originals into New York Times bestsellers in hardcover; and New York Times bestselling author Laurell K. Hamilton, a pioneer in the paranormal romance genre, who was first published by Ace before moving into hardcover at Berkley.