More than a decade ago Ang Lee’s screen adaptation of Annie Proulx’s “Brokeback Mountain” became a breakthrough film in terms of presenting gay attraction as a theme in mainstream cinema. Told in a stately, reserved manner, it nonetheless showed enormous empathy even as it proceeded to a tragic denouement.

Now Luca Guadagnino’s “Call Me By Your Name,” adapted by James Ivory, Guadagnino and Walter Fasano from André Aciman’s novel, represents a major progression along those lines—a coming-of-age story that celebrates a young man’s finding himself told with sensitivity and honesty. But unlike last year’s equally groundbreaking “Moonlight,” it’s done up in sunny, exuberant style—in Guadagnino’s characteristically extrovert fashion, abetted by the gloriously lustrous cinematography of Sayombhu Makdeeprom—even though it concludes with a recognition that love is not necessarily lasting.

The story is simple but the emotional undercurrents complex. In the summer of 1983, seventeen-year old Elio Perlman (Timothée Chalamet) is enjoying his family’s customary summer in their north Italian villa with his American father (Michael Stuhlbarg), a professor of classical archaeology, and his Italian mother (Amira Casar). Elio is a prodigy of sorts—studious, multi-lingual and adept on guitar and piano. He is also understandably engaging in preliminary sexual experimentation with his girlfriend Marzia (Esther Garrel).

Enter Oliver (Armie Hammer), the handsome, easygoing twenty-something grad student who will serve as the professor’s research assistant for the season. As usual, Elio surrenders his room to the fellow he calls “the usurper,” moving into an adjacent one with a shared bathroom.

For weeks, it seems, the relationship between the two is a succession of fumbled approaches and mixed signals. Elio is put off by Oliver’s casual self-confidence, his ability to fit in with the locals, even by the offhanded “Later” with which he departs any scene. When Oliver simply touches his shoulder, he cringes. And yet Elio is drawn to Oliver as they cycle around the village or go to an outdoor dance party; he will, among other things, take to wearing a Star of David necklace in emulation of him.

And one day, as they circle a war memorial in the town square, Elio gingerly makes a suggestion to Oliver that he follows up with a far more direct invitation as they lie in the verdant grass beside a cool stream. Oliver initially resists, and Elio himself is torn, not only continuing to engage with Marzia but ridiculing a flamboyant gay couple, Mounir (Aciman himself, in a cameo) and Isaac (producer Peter Spears), when they visit his parents. Later that night, though, Elio approaches Oliver, and they finally connect in a highly erotic but discreetly composed coupling, from a line of dialogue in which the film’s title takes its meaning.

The relationship is intense but also shot through with humor, most notably in what will surely become the film’s most memorable scene, involving a peach put to a distinctive use, which Oliver remarks on with a hilarious observation. But it is also short, since Oliver’s departure is imminent. Elio’s parents suggest that the two share a few days in Bergamo before Oliver leaves for America, and there they enjoy a passionate time together that includes a pop song that, for once, is perfectly chosen.

Through that song sequence, the film also upends one of the most disreputable clichés of the genre, replacing the usual episode of discovery and mistreatment with one of mingled joy and sadness instead. And further surprise is forthcoming in an extraordinary conversation between father and son after Elio returns home, a revealing monologue on friendship and love—with a nod to Montaigne –which Stuhlbarg delivers with a remarkable combination of simplicity and depth. A postscript set in the following winter, marked by an uninterrupted minutes-long close-up of Elio that can be seen as the visual equivalent of his father’s message, ends the film on an equally compelling note.

That final scene also represents the culmination of a performance by Chalamet that is stunning in every respect (and made more so in this instance because he has to share the sequence for a while with a pesky fly). Over the course of that single close-up the young actor registers in miniature the arc of uncertainty, happiness and heartbreak in his summer experience that he has earlier conveyed so brilliantly throughout the film. This result is one of the fullest, most compelling portraits of adolescent longing ever seen on screen.

Chalamet’s accomplishment, however, shouldn’t be allowed to overshadow Hammer’s less showy but equally impressive performance. The film truly represents a cinematic pas de deux in which each partner must support the other with impeccable timing and control, and Hammer contributes his best work ever to the equation. Stuhlbarg ‘s presence is supportive all along, but he takes center stage with that incredible final speech; the remainder of the cast is also excellent, as are the contributions of the technical crew, including production designer Samuel Dehors and costumer Giulia Piersanti. And the editing of Fasano complements Makdeemrom’s camerawork perfectly: watch that war memorial scene, and the bicycle episode that follows, where Fasano allows the empty road to linger before catching up to the men at the lake.

Some viewers may inevitably react negatively, in this post-Kevin Spacey world, to the very idea of a relationship between a seventeen-year old and a man seven or eight years older. But the story told by “Call Me By Your Name” has nothing to do with force or coercion, or any sort of abuse; it’s about an impulse on both sides that each resists until the other is ready, and the essential purity of what comes of their mutual surrender to it. (The visual allusions to the statuary of the Greco-Roman period also point to an epoch which looked upon such relationships very differently.) This is, in the end, a simple and beautiful love story—a “Brief Encounter” that happens to be gay, told with humanity and heart-wrenching truth. (The departure of the train near the close calls David Lean’s film to mind.)

It is also, of course, one of the year’s very best films.