Begin it where warm waters halt / And take it in the canyon down, / Not far, but too far to walk. / Put in below the home of Brown.

From there it’s no place for the meek, / The end is ever drawing nigh; / There’ll be no paddle up your creek, / Just heavy loads and water high.

Have you ever heard of the Lost Dutchman Mine and the Beale Cipher? How about the Oak Island Money Pit? Or the artist Kit Williams’s “Masquerade” (aka the Quest for the Golden Hare) and the magician David Blaine’s “The Mysterious Stranger” (aka the Search for the Golden Orb)? I hadn’t either. But now I know all about treasure hunts and those who plan them—especially one eccentric denizen of the American Southwest, whose self-published memoir of 2010 contains the near-incomprehensible verse-clues quoted above.

Chasing the Thrill

By Daniel Barbarisi
(Knopf, 348 pages, $28)

Reading Daniel Barbarisi’s “Chasing the Thrill: Obsession, Death, and Glory in America’s Most Extraordinary Treasure Hunt” might feel a bit like watching a Discovery Channel documentary, but the book is quite a yarn. In fact, it’s an exhaustive account of one of the oddest episodes in the crowded annals of bizarro Americana.

The impresario of “Chasing the Thrill” is Forrest Fenn, a former Vietnam War fighter pilot who made a fortune peddling Native-American artifacts and other works in arty Santa Fe, N.M. As we learn from Mr. Barbarisi, a former Wall Street Journal sportswriter and the author of an earlier book on fantasy-sports gambling, Fenn, at age 80, got the notion to hide a treasure chest in the rough country north of Santa Fe. He then printed a slim autobiography called “The Thrill of the Chase,” whose final chapter released his poetic arrows into the public imagination—verses containing nine gnomic pointers to the whereabouts of the trove of 265 gold coins, dozens of gold nuggets, plastic baggies of gold dust, a block of $1,000 bills, plus rare Mayan relics, Chinese jade and more. The 42-pound cache—secreted in a smallish 12th-century Italian lock box—was valued at up to $2 million.

Word of the Fenn lode predictably set off a gold rush of tens of thousands of ambitious, greedy and often deeply disturbed “clue solvers” who spent the next decade busting their brains and pondering maps, draining their bank accounts and risking their lives. They scoured “The Thrill of the Chase,” followed Fenn’s frequent interviews, watched and re-watched a 2013 “Today” segment he’d done, besieged his Santa Fe compound, corresponded by email, and followed a bunch of Fenn-obsessed blogs and YouTube channels. Then they traipsed through northern New Mexico, Colorado, Wyoming and southern Montana, certain that the Fenn treasure—like the mythical Land of Prester John in the Middle Ages—was just over the horizon.

The author spent years commuting from his home, job and family in Boston to the Southwest. He immersed himself in the Fenn hunters’ subculture, and pursued a number of failed solves with his wingman, Jay Raynor, a Canadian fantasy-sports wizard and crypto-currency trader. He then cozied up close to the magus, trying to get to the bottom of what motivated Fenn to launch his quest. Was he chasing a kind of pop immortality for himself? Or was he more a sadistic puppet master, savoring the spectacle of addicted hunters abasing themselves to win his favor in hopes of priceless hints to the solution? Or was he, as one cynical solver had it, simply a “media whore” hooked on attention. In any case, he writes, “Fenn had managed to mythologize his own past.”

Besides Fenn, the book is full of oddballs, among them Bill “Seattle” Sullivan, despite his moniker a homeless hunter, and one David Rice, a bearded desertphile. He describes Dal Neitzel, the loyal author of a must-read blog, as playing “Paul to Fenn’s Jesus.” Mr. Barbarisi attends the 2016 Fennboree in Santa Fe, where hunters queue up to exchange a few words with the man himself. They scuttle away as pleased as if they’d had an audience with the Delphic Oracle and just as enlightened.

The dark side of Fennworld isn’t pretty. Fenn and his family live in fear of being captured by desperate or deranged hunters. Searchers are convinced competitors are trying to steal their precious solves. At least five hunters die in their wilderness quests during the course of the book. And several women tell the author that the avuncular Fenn is actually an aging #MeToo-wannabe, pressuring female questers for naked pictures and promises of sexual favors.

Readers will soon realize that “Chasing the Thrill” is yet another shaggy-dog story, this one almost 350 pages. While stalling until the treasure is finally uncovered, Mr. Barbarisi pads out the book with extenuated examinations of every possible facet of the tale and too-long introspective passages as he interviews solvers, goes on the hunt with them, ponders Fenn’s motives and so on. There’s also lots of detail about Blaine’s orb, Williams’s hare and all the other treasure hunts, tie-in books and gimmicks. But shockingly, in all those pages you won’t find a single picture of Fenn, or the treasure chest and its contents, or the man who found it. You’ll have to resort to Google Images for that.

Indeed, the long-awaited resolution of the story is one of the least satisfying parts of the book. In June 2020, a 32-year-old former medical student from Michigan found the chest. He tried to remain anonymous, and Fenn, who died at 90 three months later, at first refused even to say where it was found. Eventually, the finder’s name—Jack Stuef—came out, and Fenn acknowledged that his treasure was unearthed somewhere in Wyoming. The author finally talks to Mr. Stuef and examines the booty in a lawyer’s office. Mr. Stuef tells him that he found the chest by getting a feel for Fenn’s psyche by painstakingly examining his writings and every utterance. But the real treasure, the detailed explanation of how he parsed Fenn’s opaque poesy—or didn’t—to hit the jackpot, is nowhere to be found in “Chasing the Thrill.”

Readers may rightly feel that, like the rest of Fenn’s hunters, they’ve been denied the big payoff they so richly deserve.

Mr. Kosner is the former editor of Newsweek, New York magazine, Esquire and the New York Daily News.