“Cool story, bro.” It’s the most trivial of visual details, glimpsed at the edge of one of “Austerlitz’s” many exactingly composed frames. Yet once you see it, it’s all you can look at: That three-word, irony-soaked catchphrase, so regularly wielded by younger generations to dismiss unwanted information, emblazoned on the T-shirt of a teenage visitor to Sachsenhausen, a former concentration camp in eastern Germany.

Surely thrown on that morning without much consideration, it’s a garment that oddly encapsulates the thoughtlessness pervading concentration-camp tourism today — as hordes of international travelers trudge through these sites of unconscionable human suffering with only a cursory interest in, or understanding of, the history on which they tread. That disconnect is silently but scorchingly addressed in Ukrainian director Sergei Loznitsa’s ingeniously simple, mesmerising documentary — a vital entry in the growing chapter of cinema evaluating the Holocaust’s present-day legacy. A stark stunner destined more for festival travel and non-theatrical exhibition than regular distribution, “Austerlitz” should nonetheless provoke its select audience into extensive philosophical argument.

Though he’s proven himself a highly accomplished narrative filmmaker, Loznitsa’s non-fiction work continues to put his storytelling impulses on a very tight leash indeed. As in most of his work — including 2014’s Ukrainian revolution doc “Maidan” and last year’s found-footage project “The Event” — no attempt is made here to lead the viewer into rhetorical conclusions via voiceover, talking heads or even a clear investigative structure. With “Austerlitz’s” strictly observational technique, what you see is entirely what you get; what you get, of course, from his camera’s patient but casually incisive recording of a day’s activity at Sachsenhausen, may vary from viewer to viewer.

Even by the director’s austere standards, the setup here is bare-bones. Filming digitally in candid, low-contrast black and white, Loznitsa positions his digital camera at eye level in an array of positions around the concentration camp grounds; in unbroken takes lasting several minutes at a time, we watch and listen to the individual visitors and tour groups as they pass by. Quite how he and fellow d.p. Jesse Mazuch have concealed their shoot is unclear, but none of their fleeting human subjects seem aware they’re being filmed. If they were, they might rethink certain actions or remarks: “Don’t worry, this isn’t the last time you’re ever going to be able to eat,” one tour guide chides her followers, in what one can only hope is unintentionally dubious taste.

Such heedless, inadvertent faux pas are the first things you notice in “Austerlitz,” as multiple tourists saunter past former prison dormitories and gas chambers with all the intellectual and emotional engagement one might reserve for a circuit of the local shopping mall: idle jokes are quietly shared, music is played on cellphones, bizarrely inappropriate selfies are taken. At one point, a young woman smilingly poses outside a chamber as her boyfriend snaps away; one can only imagine the Instagram hashtags.

Just as aggravating, in a more complicated way, is the relayed, overlapping stream of commentary from an international selection of guides, as Loznitsa dips viewers in and out of their tours — which vary wildly in tone and authority, with some appearing nearly as detached as their customers, while others go in for questionably emotive editorializing. One young American seizes the tour as an opportunity to share his own anti-spiritual life coaching with a paying audience: “Hope is simply a survival mechanism,” he lectures, speaking for all the world as if he personally survived the camp’s horrors another way.

Elsewhere, history is reduced to well-meaning but sketchily informed basics: “Petty, petty political reasons, really,” is how one guide explains the roots of the Holocaust. Given such instruction, it’s not hard to see why the gravity of the landmark evades some visitors; even when listening on more credible narration, however, “Austerlitz” is a fascinating document of how the facts of the past are filtered, edited and disseminated across cultures and generations. (These floating extracts of speech are most evocatively arranged by sound designer Vladimir Golovnitski and mixer Ivo Heger — along with a quiet cacophony of incidental hums and crackles, both natural and unidentifiable.)

Yet if there’s a tacit ruefulness to Loznitsa’s cinematic eavesdropping, this isn’t necessarily an angry film. As it becomes increasingly clear just how little connection many of these daytrippers feel to the atrocities they’re looking in on, there’s something to be said for a present — however imperfect — in which the Holocaust can feel so alien to them. The geography of the space is precisely conveyed in Loznitsa and Mazuch’s crisp, studied compositions; as the substantial crowds mill through it, with filming having evidently taken place in midsummer peak season, the film’s images eerily call to a time when the camp would have been similarly, but tragically, populated. The unstylized monochrome of the lensing likewise serves to meld past and present.

“Austerlitz” — the seemingly incongruous title of which refers to W.G. Sebald’s acclaimed 2001 novel, itself recently filmed, which also examined the conservation of tragedy for posterity — thus plays as something of a Rorschach. It feeds the views of those furious that concentration camps aren’t being observed and remembered with hat in hand, but is just as likely to stimulate the rival intellectual faction that would prefer to see them waste away unvisited.

Loznitsa’s gaze, brilliantly keen as it is, never tips his hand in this regard, even as the camera sometimes subtly undercuts the vile power these death camps once represented. It doesn’t seem accidental that one of the first images in the film is of the entrance gate from the inside, its cruel original mantra “Arbeit Macht Frei” (“Work Sets You Free”) rendered thoroughly unimposing in reverse. It reappears at the close, this time the right way round, as the buoyant crowds depart through the gates at the day’s end: Every last person in the frame has their freedom, and thankfully, they haven’t had to suffer for it. Cool story.