Postmodernism, Comedy, Quest
Comedy
This is the reason why many people who don't appreciate most of Nabokov's works still love Pnin. It's funny! If you ignore all of the creepiness and strange postmodern hallucinations going on, Pnin is thestory of an old man bumbling through life. Who isn't amused by that?
Take a line like this: "'Our friend,' answered Clements, 'employs a nomenclature all his own. His verbal vagaries add a new thrill to life. His mispronunciations are mythopoeic. His slips of the tongue are oracular. He calls my wife John'" (6.11.15). Okay, it's a little mean. Lawrence Clements is always taking a shot at poor Pnin. But didn't you chuckle? At least a little bit?
But all of this lighthearted joking is just a way to distract you from the serious stuff that lies underneath the surface of Pnin.
Quest
For example, stuff like Pnin's quest. He seems to be looking for something, some kind of meaning to life or the universe, that he never exactly finds. Here's the moment where Pnin's quest begins: "It stood to reason that if the evil designer—the destroyer of minds, the friend of fever—had concealed the key of the pattern with such monstrous care, that key must be as precious as life itself and, when found, would regain for Timofey Pnin his everyday health, his everyday world; and this lucid—alas, too lucid—thought forced him to persevere in the struggle" (1.2.41).
Whoa, dude. Who is the evil designer? We don't know. (Well, maybe we have a sneaking suspicion.) But apparently Pnin never finds this key because he keeps having these attacks well into his old age.
You could even say that Pnin's quest is one of belonging. He's been searching for a place to belong for a long time now, and at the end of the novel he has almost achieved his goal. But just at the last moment, his job and any sense of security in America is snatched away from him.
Not such a funny story now, huh?
Postmodernism
What with all the squirrels, reflections, and time-fracturing hallucinations, there is no doubt that Pnin is a postmodern novel. Pretty much every other chapter we get a passage like this:"Timofey Pnin was again the clumsy, shy, obstinate, eighteen-year-old boy, waiting in the dark for Mira—and despite the fact that logical thought put electric bulbs into the kerosene lamps and reshuffled the people, turning them into aging émigrés and securely, hopelessly, forever wire-netting the lighted porch, my poor Pnin, with hallucinatory sharpness, imagined Mira slipping out of there into the garden and coming toward him among tall tobacco flowers whose dull white mingled in the dark with that of her frock" (5.5.14).
There's a bunch goin' on up in there. Time is shuffled around, dead people appear and interact with the living, and the past is changed and modernized through Pnin's seizure-inflicted mind. Sometimes it's easy to lose track of who, what, and when of things.
Generally, postmodern techniques are used to represent what is unrepresentable. For example, how can you explain the despair of knowing that your childhood love was probably killed in Nazi gas chambers? Or how could Nabokov tell us what it's like not to have a home, when chances are the bulk of his readers don't share that experience?
By unsettling us with Pnin's hallucinations and shuttling us backwards and forwards in time, Nabokov lets us feel some of the unsteadiness that Pnin must be feeling. The addition of the strange narrator, VN, also helps us understand how Pnin must feel about his life in the United States. It's as if there were someone orchestrating all of his misfortunes. Though of course, through the magic of postmodernism, there really is.