"When I'm deep in a book, I'll hear him roaring with laughter about something. It's very off-putting," she said, giving a rare glimpse of their private life at Clarence House.
"Or I'll suddenly start weeping."
Camilla, 79, has been a keen reader her whole life. After the success of a pandemic-era book club she set up on social media, she launched a charity to promote the benefits of reading three years ago.
In Britain, the percentage of children and young people who enjoy books hit its lowest level in 20 years last year, according to the National Literacy Trust, which is now working with the government and Camilla's charity to try to turn this around.
"I left school quite young, so reading has been most of my education. You learn so much about people, about life," Camilla told the documentary, The Book That Changed My Life, which will air in the UK on Wednesday.
When Charles laughs out loud, Camilla knows he will be reading a book by Jeeves and Wooster creator PG Wodehouse. She said he also loved biographies, while she likes historical fiction and thrillers.
She said books helped her father survive more than two years as a prisoner of war in Germany in the early 1940s, an experience he then wrote a book about.
"You're not thinking of yourself when you're reading, you can immerse yourself into other people's lives and that does relieve the stress," she said.
Charles is still receiving treatment for cancer and managing the fallout from the arrest of his brother, Andrew Mountbatten-Windsor, who denies wrongdoing, as well as negotiating the relationship with his younger son, Prince Harry, who has returned from the US to live in Britain.
Meanwhile, Swan Song: Diana, My Sister, a memoir by Charles Spencer, the brother of Charles' first wife, has become a bestseller. Buckingham Palace rejected in unusually strong terms the book's version of conversations surrounding Diana's death in 1997.
