Ryan Gosling does his best to dial down his star power in “First Man,” in which he plays astronaut Neil Armstrong with unsmiling reticence and stoicism. Based on James R. Hansen’s biography of the same name, this absorbing, meticulously detailed chronicle of Armstrong’s career — culminating with the Apollo 11 NASA mission, during which he became the first man to walk on the moon — continually undercuts the story’s inherent triumphalism and mythmaking.

Like its protagonist, “First Man” doesn’t go in for theatrics or gratuitous emotion, however justified. It gets the job done, with professionalism, immersive authenticity and unadorned feeling, of which Armstrong himself might just have approved, however apprehensively.

With shaky close-ups and a deafening roar, director Damien Chazelle (working from a script by Josh Singer) never pulls back as Armstrong bounces off the atmosphere, frantically trying to bring the plane safely to ground. Of course, Armstrong himself isn’t frantic. It’s audience members who are likely to find themselves pulling back in their seats or lurching to one side or another as his unseen, collective co-pilot.

It’s a harrowing sequence, full of dizzying, disorienting close-ups and swirling gadgetry. And that radically subjective visual style will be repeated throughout “First Man,” as Chazelle crams his camera into ever more claustrophobic cockpits and capsules, as well as into the no less fraught environs of the Armstrong household.

Hewing closely to Hansen’s book, Chazelle faithfully recounts Armstrong’s bid to become a member of the Gemini team, NASA’s second manned-spaceflight program. He introduces Armstrong’s now-famous colleagues Ed White (Jason Clarke), Gus Grissom (Shea Whigham), Jim Lovell (Pablo Schreiber) and Deke Slayton (Kyle Chandler), going to exhaustive lengths to re-create such momentous episodes as the Gemini 8 flight, during which Armstrong successfully docked with another spacecraft before hurtling into a terrifying end-over-end spin. We also learn about the doomed Apollo 1 team, including White, Grissom and Roger Chaffee (Cory Michael Smith), who perished during a preflight test.

Those deaths, as well as several that came before, haunt Armstrong throughout “First Man,” which depicts him as unable or unwilling to express the mortal fear and loss that are his occupational hazards. But the sadness that trails Armstrong is nowhere stronger than in his own home. As “First Man” begins, Armstrong and his wife, Janet (Claire Foy), endure an unspeakable loss. True to form, Armstrong copes by compartmentalizing his grief, often leaving Janet and their two young sons behind, both physically and emotionally.

If Armstrong is a reluctant hero, that makes him all the more appealing in “First Man,” which is far less interested in derring-do and camera-ready cool than in depicting the discipline, focus, stamina and superhuman nerve it took for Armstrong and his colleagues to do their jobs.

Thanks to both its diffident hero and its resistance of easy romanticism, “First Man” is a surprisingly somber, occasionally inert, sometimes even off-putting enterprise. Even the visual language sends a mixed message: At times the messy verité-style realism and IMAX-scale spectacle seem to be fighting each other, with neither emerging a clear winner.

That ambivalence makes the movie a bit unwieldy, but ultimately stronger. When Armstrong, Buzz Aldrin (Corey Stoll) and Mike Collins (Lukas Haas) take their historic 1969 flight — and Armstrong takes that legendary first step and great leap — the moment carries all the more grandeur and moral force for being staged with solemnity and pockets of voidlike silence. “First Man” may not wear its heart on its sleeve. But it trusts the audience to find it on their own, in a quieter and more reflective place.