With all due respect to (yawn) Iron Man, the first great action movie of the summer has arrived, and it has nothing to do with superheroes– unless your idea of a superman is a J.D. Salinger-like Norwegian author who’s rarely seen in public. Just such a literary icon is the inspiration for Phillip (Anders Danielsen Lie) and Erik (Espen Klouman Hoiner), college-age aspiring writers who are introduced together at an Oslo mailbox in Reprise’s opening scene. They drop their respective first novels in the slot, and the world explodes with possibility.

Rarely has mailing a pair of 9x12 envelopes been treated more rapturously, but then Reprise doesn’t convey just Phillip and Erik’s youthful excitement. Writer-director Joachim Trier and co-writer Eskil Vogt take the young men’s emotions seriously, but also observe them with some detachment, and a hint of mockery. This deft juggling of tone is one reason that the movie can be described as an action flick; the film’s shifts in pitch are thrilling. So, too, are this existential romp’s speedy flashbacks, narrated asides, impatient edits, and sprinting hand-held camera. Reprise doesn’t include car-chase scenes or the like, yet it’s deliriously on the move. (Yes, Trier is a student of the French new wave, but he’s also a former Norwegian skateboard champion.)

The scenario is commonplace, yet convincingly tangled. Of the two young writers, Phillip seems the more talented; his book is published first, and to acclaim. But he enters into an obsessive relationship with Kari (Viktoria Winge), attempts suicide, and is institutionalized. Erik stays steady, and eventually his book is also published– after much second-guessing of the title, Prosopopoeia. Along the way, we meet Phillip’s and Erik’s friends, most of them somehow connected to a defunct punk band, Kommune, and also (just barely) Erik’s neglected girlfriend. Then there’s the publisher’s assistant who’s attracted by Erik’s talent, but repelled by his circle’s contempt for women. And, once in a while, an appearance by Sten Egil Dahl, the reclusive author who inspired Philip and Erik– and who, they come to worry, isn’t that great a writer, which may mean that they aren’t all that hot, either.

If Reprise wonderfully captures the giddiness of youth, it also makes room for such doubts. Barely into their 20s, Erik, and especially Philip, worry that things they love have been lost and can never be retrieved. Tentatively reconciled with Kari, Philip takes her to Paris, where he compulsively reenacts the events of their previous trip there. (Guess which sojourn is more fun.) Twice, a narrator proposes absurdly far-reaching implications for the young men’s lives and work. Yet the characters– and the movie– also can revel in a simple moment, such as the one where a party comes to life when someone puts on Le Tigre’s “Deceptacon,” and Norwegian reserve yields to American feminist synth-punk.

Endowed with a young man’s strut– Trier is 34– but also imbued with melancholy and self-aware wit, Reprise is a rare example of a talky art-house flick with the reflexes of a cheetah. The film moves beautifully, and it’s a pleasure to be carried along by its rippling action.

REPRISE ( 3 ½ ) Directed by Jaochim Trier • Starring Anders Danielsen Lie and Espen Klouman Hoiner • R, 105 min •At the Osio Cinemas.