In April 1925, a fifty-seven-year-old British explorer named Percy Harrison Fawcett trooped into the Brazilian jungle for the last time. Fawcett had spent much of his adult life under mosquito netting there, and he had become convinced that the region held the remnants of a great lost city—the stronghold of a vanished civilization. Hobbled by age and by poverty, he nonetheless convinced his financial backers to give him one last chance to prove his claims. Equipped with little except a reputation as the man whom the jungle could not kill, Colonel Fawcett and two younger companions set off on a path that would lead them deep inside the remote and rugged region known as Mato Grosso. The party was never heard from again.

Over the next several years, the world press speculated wildly on Fawcett’s fate. He had been murdered by hostile Indians; he was being held prisoner; he had lost his mind and gone native; he had been made into a god. Seven years after the explorer’s disappearance, a young British journalist set out to find him.

Peter Fleming wasn’t the first to go looking for Fawcett, but he was almost certainly the least prepared. A twenty-five-year-old literary editor at the Spectator, recently graduated from Oxford, he was a man of the pen, not the machete. He had a taste for adventure, as young men do, but had indulged it sparingly, and had little experience with map-making, Portuguese-speaking, piranha-avoiding, or any other skill that might prove useful in the jungle. His companions—wealthy sons of Eton, men of good breeding and bad judgment—were similarly young and green. “There are, I suppose, expeditions and expeditions,” wrote Fleming, and “it looked as if ours was not going to qualify for either category.”

Of the expedition, the best that can be said is that nobody died. Fleming and his cohort were slowed at the first when they arrived in the middle of a revolution, and slowed later on by argument and insurrection. Their cartographic ambitions were thwarted when they ditched their surveying equipment, finding it too heavy to carry. They found neither the lost colonel nor his lost city, although they did encounter assorted missionaries, Dutchmen, and “young men of good birth from São Paulo.” As Fleming put it: “Beyond the completion of a 3,000-mile journey, mostly under amusing conditions, through a little-known part of the world, and the discovery of one new tributary to a tributary to a tributary of the Amazon, nothing of importance was achieved.”

It did, however, produce Brazilian Adventure, Fleming’s enduring account of the misbegotten journey, which made it all worthwhile. A best-seller upon its initial appearance, the book stayed in print for decades on the strength of Fleming’s pungent wit and observational powers.

Almost eighty years later, the book is nearly forgotten, and Fleming’s reputation has been eclipsed by that of his brother, Ian, the creator of James Bond. In David Grann’s recent The Lost City of Z, which introduced the Fawcett story to a new generation, Fleming merits only one direct mention. But in its day, Brazilian Adventure was hugely influential. With a journalist’s eye and an ironist’s heart, Fleming wrote plainly and honestly about his misadventures, his unprecedented candor and self-deprecation reinvigorating a literary genre that too often trafficked in banality, fatuity, and romantic bombast.

“Truth is a perishable commodity; considerable care must be exercised in shipping it across the world,” wrote Fleming. The first truly modern travelers’ narrative, Brazilian Adventure treated the hazards of the jungle as a matter for comedy rather than terror, and suggested that the strangest things about faraway, desperate lands were often the men who rushed over to explore them.

Justin Peters is editor-at-large of the Columbia Journalism Review.