I think that any novel can be only so effective, because usually only the people who share, for the most part, the authors views will read it. Is that not why we read? Others read to feel self-reighteous outrage. That is to say that most people read with their set of beliefs already formed, and their opinion of the viewpoints of the author remains the same, only their opinion of the author changes. The only time a novel is truely effective is when a reader has no prior knowledge of the events the book is based upon, and everyone who might read Cat's
Cradle has already experienced and formed opinions about human nature.
In other words, while I thoroughly enjoyed Cat's Cradle, it did not effect my opinions because I already agreed with Kurt Vonnegut. So, although Kurt Vonnegut made excellent points, I cannot imagine that it will be very effective, because I define that as effecting change.
Can you picture someone, say, George W., reading Cat's Cradle and coming away from it a changed man? I certainly cannot, he would only lose respect for Kurt Vonnegut.
I believe that the predominant rhetorical device in Cat's Cradle was black humor. I chose black humor over irony and satire because Cat's Cradle is too absurd in places to be predonminantly ironic, and too morally ambiguous in places to be predominantly satirical. Satire is used to expose and discredit human vice, but Kurt Vonnegut seems to expose it and suggest that it has always been that way, that we need it, and that it works for us. The author introduces himself as a Bokononist, and then tells us that the Books of Bokonon begin: "All of the true things I am about to tell you are shameless lies." Indeed,