The three young actors play the central love triangle in Walter Salles' adaptation of Jack Kerouac's Beat Generation novel, an experience that has helped them appreciate why the book is considered a classic.
The tale of wannabe writer (and Kerouac surrogate) Sal Paradise and his friend Dean Moriarty crisscrossing the United States in search of freedom and the elusive "it" was published in 1957. But Stewart said the way it captures the heady feeling of young adulthood is timeless.
"You're so filled with something that is hard to identify at this age," said the "Twilight" star, who plays Dean's teenage bride Marylou, a free spirit torn between the lure of adventure and desire for a more settled life.
"You're just bursting, and (the characters) value that so much," said Stewart, who is just 22 herself. "They don't ignore it. That celebration of youth and exploration is just something that you envy.
"I read it right at the point when I was about to get my (driver's) license, and I thought, wow, I want to meet people who push me the way people push each other. I wanted to be more like them."
The director said he was determined to cast Stewart even before "Twilight" made her a star, after he heard raves about her performance in Sean Penn's 2007 Alaskan drama "Into The Wild."
"I remember writing down the name," Salles said, "so I wouldn't forget it."