War seems like an abstraction in this occasionally affecting adaptation of Meg Rosoff’s novel about a 21st-century conflict that rains down death on civilians.

The title, “How I Live Now,” suggests a certain distance, and that’s rigorously maintained in the movie. Thousands of Londoners may be wiped out in a huge explosion, martial law may be declared, society may be disabled, but the emotional impact seems curiously muted.

The viewpoint is that of a bratty American teenager, Daisy (Saoirse Ronan), who is sent for the summer to live with her aunt (mostly absent) and country-bred cousins, including 17-year-old Eddie (George MacKay). In love at first glance, Daisy and Eddie are clearly headed for trouble, and much of the movie plays like a violent backdrop to their forbidden affair.

When war breaks out and the woods are filled with terrorists and soldiers, the conflict is essentially an impediment to their relationship. Once they’re sent off to different camps, they pledge to meet again. Only the possibility of their reunion carries much dramatic weight.

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Director Kevin Macdonald, who guided Forest Whitaker to an Academy Award for “The Last King of Scotland,” gets a dedicated performance out of Ronan, who was nominated for an Oscar for “Atonement.” Daisy is not always credible as a character who becomes a survival expert, but the fault is with the script, not the actress.

Reminiscent at times of the Civil War love story “Cold Mountain,” the infatuation has barely begun when the lovers are separated, and MacKay mostly makes it work. Framed like the cover boy on a swoony romance novel, he demonstrates a comfort level with his trained hawk, farm chores and livestock that never feels forced.

John Hartl: johnhartl@yahoo.com