Miners have a rule: Nobody walks anywhere alone. A slab of rock can peel off suddenly and imprison a man for days. Or a miner can step, without the warning of a shadow, into a fatal crevasse. The buddy system is an expression of the profession’s perils and, ironically, also the limits of its safety: What happens when every man’s life is in danger?

That’s the question on Héctor Tobar’s mind in his chiseled, brooding new book, “Deep Down Dark.” It tells the much-covered 2010 story of 33 Chilean miners trapped underground for 69 days. Tobar, a Pulitzer Prize-winning journalist and acclaimed novelist who lives in Los Angeles, spent four years interviewing “los 33,” their families and rescuers, chipping away at the mystery of how these men survived for more than two months, “suddenly and unexpectedly close to death, but still in control of [their] fate.”

That fate, of course, is well-known. On Aug. 5, 2010, a chunk of mountain 550 feet tall and twice the weight of the Empire State Building collapsed within the San José Mine, sealing the men inside. They were more than 2,000 feet underground. Seventeen days later, the Chilean government, with help from NASA and numerous international bodies, finally confirmed via a drill-fed camera that all the men were alive.

But it would take more than two months for the miners to see daylight again. And because of a pact — and later a contract with Tobar — the men revealed to the public only selected anecdotes about their 69 days under the earth’s surface, and nothing of the 17 dark days preceding the drill’s breakthrough.

With the ending given away, these early moments of dread and shadow are the book’s real rewards, narrated by Tobar in biblical tone: “[They were] trapped inside a kind of metaphor about the cycles of life and death, halfway on that metaphorical journey from the sunshine of being fully alive to the permanent blindness and deafness of death.”

“Deep Down Dark: The Untold Stories of 33 Men Buried in a Chilean Mine, and the Miracle That Set Them Free," by Héctor Tobar. (FSG)

Underneath guilt and grief, many survival books, such as “Into Thin Air ” and “The Perfect Storm ,” reveal hubris at their core. But “Deep Down Dark” doesn’t concern itself much with fault or fate. Instead, Tobar splits his story into three sections, each claustrophobic and psychologically piercing in its own way: adventure, prison, post-crisis. That he has so vividly reconstructed a life-threatening event remembered differently by 33 minds is a mountainous feat of reportage.

A less restrained writer might have tried to lard this story with melodrama. Instead, Tobar flakes off the slimmest details, amassing some unbelievably immediate and terrifying sentences that almost rumble off the page: “At 1:40 p.m., three men are using [a wrench] to tighten the last two bolts on one of the squat machine’s five-foot-tall wheels when they hear what sounds like a gunshot. A moment later, they are knocked off their feet by a blast wave, and then enveloped by the sound of falling rock, and the walls around them begin to shake, and stones the size of oranges are falling around them.”

It’s hot, dank and dark down there, and as time goes on, everyone prays, mostly for food. Many of the book’s early pages depict the men dreaming of barbecue and cold beers. Hunger leads some of them to break into an emergency cabinet and gorge themselves. The group as a whole is left with only some children’s cookies and cans of tuna and salmon.

Even worse for some of the miners, however, was the darkness. Tobar describes this ordeal as if he were down there with them, seeing as little as they do, recording the events through the dim echo of voices. Each miner “finds himself inside a patch of blackness,” with only the light of other men’s helmets to navigate by.

Only after the drill breaks through, bringing with it the chance of escape, does the cave shift from a crypt to a prison. The hole is big enough to allow for the introduction of glucose gels, so the hunger is finally allayed. But when the men learn that their plight is getting 24-hour news media coverage, they begin to argue over hierarchy and the right to tell their story. At this point, the book becomes a psychological study of lockup, in which Tobar does justice to both the setting and the human dynamic. The group loses its solidarity, alliances form, the first fight breaks out. “It’s cash fever,” he writes.

Once rescued, some men suffered in new ways. Edison Peña, whose run in the Nov. 7, 2010, New York City Marathon became a symbol of perseverance, battled with alcoholism. Others suffered from depression and post-traumatic stress disorder. As Tobar works his way through each miner’s recovery, the TV headlines recede from our memory, and a more delicate series of portraits emerges.

There’s no unified story of survival, Tobar seems to be saying, only each man’s story. Months after the rescue, one of the miners “sits in the living room in the dark with the mining lamp on, as if he were back inside the caverns of the San José, listening to the distant thunder.”

Shannon’s work has appeared in Slate, the New York Times Magazine and Running Times.

DEEP DOWN DARK

The Untold Stories of 33 Men Buried in a Chilean Mine, and the Miracle
That Set Them Free

By Héctor Tobar

Farrar Straus Giroux.
309 pp. $26