 In the 1950s he was a leader in bringing science fiction out of the low-paying and less prestigious "pulp ghetto".Most of his works, including short stories, have been continuously in print in many languages since their initial appearance and are still available as new paperbacks decades after his death.He was at the top of his form during, and himself helped to initiate, the trend toward social science fiction, which went along with a general maturing of the genre away from space opera to a more literary approach touching on such adult issues as politics and human sexuality.