Leaving kids to face hellacious problems without adult assistance (read: interference) is one of the signatures of teen literature. But the YA adaptation “How I Live Now” (2013) takes this to extremes, imagining how its disaffected heroine (Saoirse Ronan) would cope, and change, when confronted by the sudden societal ravages of a terrorist-triggered nuclear war. Still, however her world is rocked, director Kevin Macdonald (“Touching the Void,” “The Last King of Scotland”) makes this very much an acoustic tale. Ronan darkens her ethereally bright gaze with punk-chick eyeliner to play Daisy, a sullen American girl shipped off to relatives in the English countryside. It’s an idyllic setting insulated from vaguely referenced near-future geopolitical tensions, but Daisy is miserable all the same, giving her well-meaning, minimally supervised cousins (notably Tom Holland of “The Impossible”) nothing but attitude. Then the oldest of the group, hunky Eddie (George MacKay), finally gets her to open up — to new experiences, to connection, to love. When the bomb drops and the world goes to hell (again, vaguely), displaced Daisy channels her edgy side into a quest to reunite with Eddie and right their upended life. The story’s ultimately hopeful message doesn’t quite come across (and the unaddressed kissin’ cousins dynamic is apparently something we’re not supposed to question, period). But it’s an intriguing dark turn from Ronan (“The Host”), and an interesting variation on Macdonald’s penchant for fascinating, unnerving visual and thematic perspectives on the world. Extras: cast and crew interviews spotlight Boston-bred, United Kingdom-based source novelist Meg Rosoff. (Magnolia, $26.98; Blu-ray, $29.98; available now)
GAME OF THRONES: THE COMPLETE THIRD SEASON (2013)
The battling families of Westeros continue to duke it out — and still find time to weave Emmy-nominated Diana Rigg into their rich fantasy tapestry, among other new diversions. Extensive extras include a Blu-ray segment spotlighting the Twitterverse-jolting episode “The Rains of Castamere,” plus a featurette introducing Rigg’s Olenna Tyrell and other series newcomers. Among the 12 audio commentaries are tracks from series creators David Benioff and D.B. Weiss, “Thrones” author George R.R. Martin, Lena Headey, Michelle Fairley, and Richard Madden. (HBO, $59.99; Blu-ray, $79.98)
THE SUMMIT (2013)
It might not be as insanely arduous as trying to scale the 28,000-foot Himalayan peak K2, but making a documentary about the climb — specifically, about a 2008 expedition gone horrifically wrong — is plenty ambitious. First-time director Nick Ryan isn’t entirely up to the challenge, but he does deliver some dramatic and visual highs in the attempt. There are so many different players giving so many confusing, slightly conflicting accounts of their all-but-unknowable ordeal, the specifics remain a logistical muddle, despite some impressive climbing reenactments. (IFC Films, $24.98; available now)Tom Russo can be reached at email@example.com.