Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
(Exposition) Initial Situation
Pnin is Pninian
We meet Professor Timofey Pnin, our lovable and totally awkward protagonist. All you need to know about his situation is that he's a Russian émigré, he's still not quite at home in America, and other people think he's pretty weird. Basically everything else in the novel derives from these facts.
Rising Action (Conflict, Complication)
A Lousy Life For Pnin
So we already knew that Pnin is a weird guy, but what we didn't know is how much his life sucks. He has no stable home. No friends outside of Russian émigré's that he sees once a year. His first wife tricked him in order to get into America, and also wants him to pay child-support for a kid who's not his own child.
The list could go on. But basically if you can imagine it, it's probably happened. That's more than enough conflict to complicate this story. Sure, he's got some pleasant moments. But between nasty ex-wives, getting evicted, the occasional heart attack and horrible memory, and getting made fun of by basically everyone, we spend most of the book feeling sorry for him. And kind of wanting to join in with the mockery.
Climax (Crisis, Turning Point)
Bad News: You're Fired!
There was probably one thing you couldn't imagine. As bad as everything was, you couldn't imagine that he would get fired from his university, right? Wrong. All of the terrible things that have happened to Pnin culminate in his getting the boot from Waindell College, which results in him not being able to finally get a home. This is definitely a game changing moment.
Falling Action
Wait, Whose Story Is It?
VN, our omnipresent and kind of creepy narrator tells his version of Pnin's story. Normally, during this part of a story, loose ends are wrapped up. However, here things just get more and more complicated as time goes on. This happens after the climax, and leads up to Pnin getting out of Waindell, so it's definitely a fall in more ways than one.
Conclusion
Goodbye Pnin, hello VN!
So how does this weird story end? Just like it seems that Pnin was kicked out of his own story by VN, the same guy kicks him out of his university position and takes his place. The last image we have is of Pnin driving away into the sunset. So long, Pnin!