I've read the great majority of his stuff since he wandered into and out of the science fiction ghetto many years ago. For a pessimist he was often funny. He created the phrase "So it goes" echoed every time a character died in Slaughterhouse Five that was picked up by others including Linda Ellerbee.
Gore Vidal once called him America's worst writer. Vonnegut sometimes indicated he agreed with that assessment: "Jesus-if Kilgore Trout could only write!" Rosewater exclaimed. He had a point: Kilgore Trout's unpopularity was deserved. His prose was frightful. Only his ideas were good." Rosewater, was a great character also used in other novels. Ditto for Kilgore Trout, an alter-ego of Vonnegut.
Another interesting poor writer, Phillip Jose Farmer, created a SF novel by Kilgore Trout and a lot of people didn't get the joke. So it goes.
Mother Night was one of his best novels for me with a simple dramatic moral effectively illustrated. You are what you pretend to be so you must be careful who you pretend to be. Slaughterhouse Five and Sirens of Titan may be his best more conventional SF related works overall.
Vonnegut never attained the literary esteem of JD Salinger, another favourite among young people, and his work retains the stigma of being an adolescent or campus taste. Nonetheless, his snappily expressed disaffection with the ways of what passes for civilisation made him a spokesman for an America that had lost its way after Hiroshima and Vietnam. Humane, funny, quotable, and disarmingly modest, it is as hard not to respect Vonnegut the man as it is to unreservedly admire all of his work. The individual of whom JG Ballard once said "his sheer amiability could light up all the cathedrals in America" is no more. So it goes.Reflecting back on his writings now they may have influenced me as much or more than Robert Heinlein's works. RAH is in many ways the antithesis of Kurt Vonnegut. So it goes.
Word: Kurt Vonnegut.