Cat's Cradle employs a first-person central narrative style to embody the heterodiegetic…
Wow, sorry about that. We were momentarily possessed by the spirit of an angry English teacher. What we were trying to say is that we explore the novel's story and world through the main character's perspective.
Every bit of detail we get in Cat's Cradle we receive through John—our main character and narrator. Where he goes, we go. What he experiences, we experience. You can tell this is the case because the story is presented with the "I" pronoun. For example:
"Go get your clarinet," urged Newt. "That always helps."
I thought at first that this was a fairly comical suggestion. But then, from Angela's reaction, I learned that the suggestion was serious and practical. (79.21-22)
Notice how Newt isn't really speaking. John hears Newt and then reports back to us what was said. In fact, no character other than John can technically speak for him or herself in Cat's Cradle.
Also, you'll notice from the example that we only ever get John's reaction to any situation. It may seem like we're getting some of Angela's thoughts, but this is actually John telling what he thinks Angela thinks. We have no actual way of knowing how Angela feels—because everything is filtered through John's perspective.