The shortness of my review on this essay is because I don’t believe I’ve actually ever read a complete novel by Kurt Vonnegut.
Review: “Locked in the Slaughterhouse: The Novels of Kurt Vonnegut”, Brian Stableford, 1976, 1995.

Stableford looks at Vonnegut’s novels, both science fiction and non-science fiction, from 1952 to 1973 and sees them as all thematically linked and about Vonnegut trying to make sense of his life. The humor to be found in his novels is black and acidic. The novels are not meant to be funny but tragic:
The works of Kurt Vonnegut are the works of an incompletely unhappy man: a man whose experience in Dresden might have shattered all faith he ever had in life or humanity, but who somehow retains an essential sympathy.