clipped from edition.cnn.com Philip Jose Farmer, science-fiction writer, dies at 91 (CNN) -- Author Philip Jose Farmer died in his sleep Wednesday, according to a message on his Web site. His most popular work was his "Riverworld" series, written in the 1970s. Joe Lansdale, a critic, writer and friend of Farmer's, credited Farmer with changing the face of science fiction. Farmer was one of a handful of writers to win the lifetime achievement award from the World Fantasy Society and the Grand Master Award presented by the Science Fiction Writers of America. Farmer's latest books were published by Subterranean Press. His last novel, "The City Beyond Play," was published in 2007. Critics say Farmer, who was born in Indiana but spent the rest of his life in Peoria, Illinois, was the first author to address adult sexual themes in science-fiction novels.