I was at a bar last night. Doesn't matter where because I'm lying. Louis C.K.
The tone of Cat's Cradle is more stand-up comedy routine than traditional novel. You know how these stand-up comedy routine generally go. The comedian walks up to the mic and says, "So I was at this bar and…." He then goes on to tell a very funny story.
Why is it funny? Because it's true—if you'll pardon the cliché. It doesn't matter that the particular story is made up, because truth isn't in whether or not the comedian went to the bar. The truth is in the way the story is told, the words chosen, and, ultimately, in how the jokes express something hilariously and uncomfortably true about this crazy world we live in.
Here's an example of the stand-up tone at work in Cat's Cradle. In Chapter 73, Philip Castle tells John a story from his childhood. A ship wrecked off San Lorenzo's coast, washing up wicker chairs and rats onto the island. The rats brought with them bubonic plague. Philip's father attempted to save the natives, but most died. In one room filled with dead bodies, Philip's father took his son aside and said, "someday this will all be yours" (73.44).
Okay, so that joke isn't exactly LOL material. But it's funny, because it plays off of the typical story setup of a father presenting his son with his inheritance. Only this time, the son doesn't receive a kingdom or a successful business but a world filled with death and disease.
Did this story really happen? Of course not: Cat's Cradle is a work of fiction. But we recognize the truth in the grim story. Fate and death is really all we can expect in this world. Grim? Sure. Pleasant to dwell on? Not exactly. True? Sadly—or perhaps laughably—so.