Saoirse Ronan in Belfast, Northern Ireland

Books written from a child’s point of view are notoriously difficult to translate to film. Adult authors may be able to capture in words how the world looks to a child, but ironically, it’s the rare child actor who is able to convey that naïveté, uncertainty and wonder on cue. Such was the challenge in adapting two recent best-selling literary novels: Ian McEwan’s Atonement (to be released in December) and Alice Sebold’s The Lovely Bones (which Peter Jackson is currently shooting), both of which feature adolescent girls dealing with some very mature themes. As it happens, the two highly anticipated films will star the same actress: 13-year-old Saoirse Ronan, who lives in the village of Ardattin, south of Dublin. (Her first name is pronounced “ser-sha.”) She has not read either book. “I might not be old enough,” she says.

For Atonement, director Joe Wright had already cast Keira Knightley and James McAvoy as the star-crossed lovers but knew it would be difficult to find his young Briony. The ability to act is “very rare amongst people that age,” he says. After considering “thousands and thousands of kids,” he came across Ronan’s audition tape and realized his search was over. Says Wright, “She imagines what it’s like to be that person and plays it.”

“With Atonement, I had to kind of test myself expressing different emotions and stuff,” explains Ronan, whose father, Paul, is a television actor in Ireland. “It was the first time that I had done anything like that.”

And there are only more challenges ahead. The actress, who also recently wrapped City of Ember, a children’s film starring Bill Murray, says she has no doubts about her chosen career: “I really want to do this for the rest of my life. Because once you get a taste for it, you can’t really brush it aside.”