A self-described religious skeptic and freethinking humanist, Vonnegut used protagonists such as Billy Pilgrim and Eliot Rosewater as transparent vehicles for his points of view.
He lectured regularly, exhorting audiences to think for themselves and delighting in barbed commentary against the institutions he felt were dehumanizing people.
"He was a man who combined a wicked sense of humor and sort of steady moral compass, who was always sort of looking at the big picture of the things that were most important," said Joel Bleifuss, editor of In These Times, a liberal magazine based in Chicago that featured Vonnegut articles.
Some of Vonnegut's books were banned and burned for suspected obscenity. He took on censorship as an active member of the PEN writers' aid group and the American Civil Liberties Union