I just received a collection of Vonnegut books, so I've been reading them. From the prologue to Jailbird:
John Figler is a law-abiding high-school student. He says in his letter that he has read almost everything of mine and is now prepared to state the single idea that lies at the core of my life's word so far. The words are his: "Love may fail, but courtesy will prevail"
This seems true to me--and complete. So I am now in the abashed condition, five days after my fifty-sixth birthday, of realizing that I needn't have bothered to write several books. A seven-word telegram would have done the job.