He apparently was inspired by Thomas Mann to become a writer. Mann had come to his university and had lectured on writing: "Writing ... was the only worthwhile attainment, the surpassing experience, the exalted struggle, and there was no way to write other than like a fanatic."
"Without fanaticism, nothing great in fiction could ever be achieved," concluded Nathan. But soon, the daily struggle of filling up the next page bored him to death.
So, off he goes to Univ of Chicago to enroll himself in medical school. On the way, he pretends to be a porn magnate, a competitor to Hugh Hefner whom he despises, and wisecracks with an unsuspecting co-passenger. He does the same with the female chauffeur of the limo that he hires at the airport. Quite hilarious!
I loved this passage on marriage from an early part of the novel:
"Marriage had been his bulwark against the tremendous distraction of women. He'd married for the order, the intimacy, the dependable comradery, for the routine and regularity of monogamous living; he'd married so as never to waste himself on another affair, or go crazy with boredom at another party, or wind up alone in the living room at night after a day alone in his study. To sit alone each night doing the reading that he required to concentrate himself for the next day's solitary writing was too much even for Zuckerman's single-mindedness, and so into the voluptous austerity he had enticed a woman, one woman at a time, a quiet, thoughtful, serious, literate, self-sufficient woman who didn't require to be taken places, who was content instead to sit after dinner and read in silence across from him and his book."