An American author of science fiction and horror, he is best remembered for his novel, More Than Human, which won the 1954 International Fantasy Award. His other works include I, Libertine and Microcosmic God.
He worked as a door-to-door refrigerator salesman before publishing his debut novel, The Dreaming Jewels, in 1950.
He was the recipient of both Hugo and Nebula Awards.
He married three times and had a total of seven children.
He was related to Ralph Waldo Emerson.