"Young-adult literature" did not technically exist when I was a young reader, so it's kind of amazing to see just how huge a piece of the publishing pie the broad genre has become. I've been trying to decide what I think the definition of a young adult novel is, and I think the best version of it has to do with fiction that captures that moment where someone is wrestling with their identity and defining their place in the world. It often seems to be concerned with someone learning a sense of personal responsibility, and while the general trappings of the genre can be ridiculous and exaggerated, like zombies and vampires and werewolves, there is something genuine that they seem to address when they're done well.

Meg Rosoff's "How I Live Now" was well reviewed and won several awards, and while it was a success, no one would ever look at this and think that it's going to become the next "Twilight" or "Hunger Games." Wisely, instead of trying to shoehorn Rosoff's small and delicate book into the wrong shape, the script by Jeremy Brock, Tony Grisoni, and Penelope Skinner is a modestly-scaled story, and Kevin Macdonald has made a movie that feels like a largely internal journey, a window into the heart of Daisy (Saoirse Ronan), an angry girl who is on the verge of becoming an angry woman before she is sent for a summer to a relative's farm. It's often melodramatic to call something "life-changing," but that's very true in this case, and it's handled with genuine grace and subtlety.

Macdonald has had an interesting career as a director. "The Last King Of Scotland" featured an Oscar-winning performance from Forest Whitaker, and when that happens, sometimes you get immediately shoehorned into the role of "an Oscar filmmaker," which seems to me to be just as narrow a trap for a director as any other. Macdonald seems determined to do more than that, though. Look at his films like "Touching The Void," "One Day In September," or "Marley," and he's not a guy who can be easily pinned down. "The Eagle" and "State Of Play" seem like pretty radically different types of films. In some ways, I would consider "Life In A Day" his most personal movie, which seems weird since it's made up of material shot by people around the world. Macdonald's work is driven largely by a curiosity about the details of people's lives, and that's exactly what "Life In A Day" is about. Macdonald's jumps from genre to genre and from style to style seem to serve that curiosity as he makes movies as a way of exploring all these other viewpoints and voices.

When Daisy is sent from New York to stay with her distant relatives, she is like a clenched fist. She's not happy about the situation, and she's a city kid who finds pretty much everything about life in the remote UK countryside miserable. She is gradually won over, though, by the sheer force of nature represented by Isaac (Tom Holland), Edmond (George MacKay), and Piper (Harley Bird). Their mother, Aunt Penn (Anna Chancellor) is constantly working, and she's got some sort of government job that has her right in the middle of what seem to be an increasingly volatile situation that unfolds at the edge of the story, in passing, on screens we occasionally see in the background. When things finally do boil over, I like how Macdonald keeps the perspective focused on Daisy and her cousins and what's happening with them.

I recently found myself hitting a saturation point for "this is how things will be after the world falls apart" stories, mainly because they all seem to lean on the same few tropes. I get weary watching movies about how things will get all rapey and "Lord Of The Flies" after the world "ends," and so few of the films have anything new to say about those ideas that I don't know why anyone would want to make them. Here, the point isn't how the world changes, it's how Daisy changes, and that's what makes the film work. Ronan is a tremendous young actor, and she manages to make Daisy's evolution seem completely honest and real. Tom Holland, who played one of the sons in last year's "The Impossible," is good here as the younger brother, and little Harley Bird made me laugh a lot as chipper little Piper. George MacKay has probably the hardest role in the film, playing the quiet Edmond, the older brother who becomes the most important person in Daisy's life. It would be very easy for this role to swallow a young actor, but he makes silence compelling and human and dynamic, and his chemistry with Ronan is very easy and natural.

Franz Lustig's photography is a big part of what works about the movie. It makes a strong case for the natural beauty of the countryside where Aunt Penn's family lives, and when things go wrong and Daisy finds herself on a cross-country journey on foot, he captures the stark difficulty of the land and the fear that it can create in certain circumstances. Editor Jinx Godfrey and composer Jon Hopkins also contribute mightily to the dreamlike internal quality of much of the film. I feel like this is a great example of a film that manages to find a visual language that captures the same things that the prose of the book did so well, and it is a lovely film that proves that starting with a young adult novel does not mean you have to aim low with the finished film.

"How I Live Now" is in theaters on Friday.