Okay, Vonnegut's 'Cat's Cradle'. If you're about to jump in, I'd zero in on the narrator, John. He's also called Jonah, which is a whole biblical thing he kind of pokes at himself. He's our guide, but he's not the center. The real chaotic energy comes from Dr. Felix Hoenikker, the dead scientist who basically invented the apocalypse with ice-nine. You learn about him through everyone's messed-up memories.
Then you've got his kids: Newt, the midget painter who's seen too much; Angela, who treats the doomsday weapon like a family heirloom; and Frank, who's off selling it to a banana republic dictator. That dictator is 'Papa' Monzano, and his idealistic daughter, Mona, who John gets fixated on. Honestly, the holy man Bokonon, who never actually appears, might be the most important. His made-up religion and calypsos frame the whole nihilistic joke of the book.