"You probably shouldn't be talking about it, you probably should be doing it," the 73-year-old author told Winfrey in a rare TV interview, which aired Tuesday on "The Oprah Winfrey Show."
The press shy McCarthy said he has nothing against the media, but that he doesn't believe he should be talking about what he does — a trait Winfrey illustrated with a story about how McCarthy, when he had no money years ago, refused a speaking engagement that would have paid him $2,000.
"You work your side of the street, I'll work mine," he said in an interview that was taped at the Santa Fe Institute in New Mexico.
The interview follows Winfrey's announcement in March that she had chosen McCarthy's "The Road" for her book club.
On Tuesday's show, Winfrey announced that "Middlesex," a Pulitzer Prize-winning novel by Jeffrey Eugenides, was her latest selection. Published in 2002, the book is an epic about a Greek-American who is a hermaphrodite — someone born with both male and female sexual organs.
"I promise it will grab you from the first sentence," she said.
During Winfrey's interview with McCarthy, the author said that while typically he doesn't know what generates the ideas for his books, he can trace "The Road" to a trip he took with his young son to El Paso, Texas, about four years ago.
There, standing at the window of a hotel in the middle of the night, his son asleep nearby, he started to imagine what El Paso might look like 50 or 100 years in the future.
"I just had this image of these fires up on the hill ... and I thought a lot about my little boy," he said. He wrote some of his thoughts down and didn't really think about it again until he was in Ireland a few years later and the novel came to him.
"There was a book, and it was about that man and that little boy," he said.
"The Road," this year's winner of the Pulitzer Prize for fiction, is about a father and his son as they wander through a barren post-nuclear landscape. It is dedicated to McCarthy's son, John Francis, and the author acknowledged that he wouldn't have written it had he not had a son.
Having a child as an older man also had its effect on McCarthy. "It wrenches you up out of your nap and makes you look at things fresh," he said. "It forces the world on you, and I think it's a good thing."
Winfrey was clearly fascinated with McCarthy's life, particularly the time when he was so poor that he once was tossed out of a $40-a-month hotel because he couldn't pay his bill.
He told a story of living in a "shack in Tennessee," having so little money that he could not afford to buy toothpaste when he ran out, only to discover a free sample of toothpaste in his mailbox.
"Just when things were really, really bleak something would happen," he said.
Winfrey could also not seem to get over how little McCarthy cares about success, that it didn't matter to him that millions of people read his books now compared to a few thousand in years past.
"You are a different kind of author, let me tell you," she said, chuckling.