Later I bought the Ballantine hardcovers, and even later bought the cover painting for Citizen in Space from Richard Powers.  I still have it and it is one of the chief ornaments of my art collection.  I really like the AAA Ace Decontamination Agency stories ("Ghost V" may be the best of them, although "The Lifeboat Mutiny" is very fine as well.  You might be pleasantly surprised if you can find a copy of the '50s radio adaptation of Dimension X, if I recall correctly.  The sound track features fine musical jokes.).  Those stories, with their twisty plots and good humor are in some ways the foundation of Sheckley's early popularity---his early mastery was in part a mastery of the plot twist.  I think "The Prize of Peril" and "The
 Seventh Victim" are important SF stories, and I read Sheckley stories and novels that in many ways just got better and better until the late 1960s (remember the novels Mindswap and Dimension of Miracles?) when they sort of stopped for a while.  Not entirely, but almost

I later learned that he had dropped out and gone to the island of Ibiza.  He came back in the 1970s and published some things I don't find so memorable as the earlier stuff.  He became the fiction editor of Omni in the early 1980s, got remarried at least once, left New York again and ended up in Portland, Oregon for nearly twenty years, mostly married to the writer Gail Dana, during which time he hit his stride again in short fiction, including publishing some stories I have included in my Year's Best anthologies over the last ten years.