A high school English teacher spoiled me by having us read Cat's Cradle instead of the more common/historical Slaughterhouse Five. Great kickoff to a lifelong love of his satire.
Cat's Cradle shows both the horror and absurdity of Nuclear War. It's unbelievable to imagine losing all the world's water and yet anyone can fathom how actually horrific it would be. This is Vonnegut's gift. Hard to imagine another write who can make you feel knowledgeable and challenged but also doesn't require some deep subject/stylistic knowledge of the allegories to be in on the joke.
Breakfast of Champions is also a must read. No book has ever made me laugh out loud both at the deadpan delivery and absurdity.