Dr. Wilbur Daffodil-11 Swain, centenarian, the last President of the United States, King of Manhattan, and one-half (along with his sister, Eliza) of the most powerful intelligence since Einstein, is penning his autobiography. He occupies the first floor of a ruined Empire State Building and lives like a royal scavenger with his illiterate granddaughter and her beau. Buffeted by fluctuating gravity, the U.S. has been scourged by not one, but two lethal diseases: the Green Death and the Albanian Flu. Consequently, the country has fallen into civil war. (Super-intelligent, miniaturized Chinese watch the West self-destruct from the sidelines.) Swain stayed at the White House until there were no citizens left to govern, then moved to deserted New York City, where he writes a thoughtful missive before death.
In Slapstick, Vonnegut muses on war, man's hubris, and the awful, crippling loneliness humans are freighted with--but, miraculously, the book still manages to delight and amuse. Absurd, knowing, never depressing, Slapstick kindles hope--for the possibility of wisdom, perhaps; for human resiliency, surely.
It's best to end with a quote from the prologue wherein the author discourses on The Meaning of It All, or at least This Book: "Love is where you find it. I think it is foolish to go off looking for it, and I think it can often be poisonous. 
I wish that people who are conventionally supposed to love each other would say to each other, when they fight, 'Please--a little less love, and a little more common decency.'" 
Amen.