(CNN) -- Shailene Woodley isn't just the lead actress in "The Fault In Our Stars." She's one of the book's original fans.
Long before she landed the role of Hazel Grace, a bright 16-year-old facing cancer, she sent the novel's author, John Green, an impassioned, lengthy e-mail rallying for "The Fault In Our Stars" to become a movie.
"I didn't say I needed to be Hazel," Woodley said at the movie's New York premiere on June 2. "I said I needed this movie to get made. Because I knew that it would change the lives of millions of people."
If the movie version of "The Fault In Our Stars" is anything like the book, Woodley will soon be proven right. The adaptation, now in theaters, is faithful to its beloved source material, which chronicles the romance between two cancer patients with humor, intelligence and honesty. Author Green had already amassed a fan base when "The Fault In Our Stars" was released as a novel in January 2012, one devoted enough to earn him the title of "The Teen Whisperer."
But "The Fault In Our Stars" has stretched far beyond its intended young adult demographic, selling millions of copies and sticking to The New York Times Young Adult best-seller list for 78 weeks.
Time magazine didn't name it "The Best YA Novel of 2012"; it recognized it as the year's best book, period, the kind of endorsement Woodley could get behind.
The 22-year-old actress, who is developing a reputation for pushing back against Hollywood's rules, recently explained to New York Magazine the impact she thinks "Fault In Our Stars" could have.
"In 'Fault,' I am trying to rewrite what a female lead can look like," Woodley said. "You've never seen a woman on the poster for a movie with a cannula in her nose."
Although Woodley said she wasn't gunning for the role of Hazel when she wrote Green, the author remembers that exchange a bit differently.
"The letter was extremely long, like 40 pages long, and ... I didn't technically know who Shailene Woodley was," he said. "So I just responded like, 'That's such a lovely e-mail! Thank you so much! But I am not a casting director.' And then when I saw her audition, of course I was horrified that I had not written her back and said, like, 'Please! Please! Be in our movie!'"
Of course it's unlikely that Green, who calls Woodley "a gift" to the film, would have had to beg. Woodley, who's gone from ABC Family's "The Secret Life of the American Teenager" to high-profile projects like "The Descendants" and "Divergent" in the blink of an eye, was game for the role, chopping off her long hair to accommodate the part.
In the process, she gained something as well: "a deeper sense of gratitude" for life.
"On this beautiful day, there's kids at home in bed hooked up to chemo machines," Woodley reflected at the movie's June 2 premiere. "There's no way to justify it. So, really, it taught me a deeper sense of gratitude and a deeper sense of appreciation for these small palpable moments, because they're the only thing that we're guaranteed."
CNN's Joan Yeam contributed to this report.