Flagship brew Alpha King,a pale ale, is typical of the Three Floyds approach: Even this milder style is unusually full-flavored. (Lindsay Gallup)

It is one of the beer world’s biggest mysteries: How did a small brewery at the end of a small industrial park in a small town near Chicago become the best brewery in the world?

Three Floyds Brewing, beneath a water tower in Munster, Ind., has been making the best beers on the planet for four of the past five years — at least according to the more than 1 million beer reviews logged each year on RateBeer.com. (In 2008, it slipped to second place.) Of course, as Three Floyds sales manager Lincoln Anderson put it, “That’s really cool, but what does it really mean?”

Here’s one answer: It means Three Floyds has won over the beer geek elite, the sort of guys who frequent RateBeer, drive hundreds of miles to snag limited releases, and trade rare bottles like baseball cards.

It also means that these beers, when gray-market entrepreneurs fill a van or U-Haul and schlep them to the District, sell here for between about $20 and $40 per 22-ounce bottle. And it means that maybe, just maybe, Three Floyds has stumbled upon some sort of secret truth about how the beer world works, a secret that accounts for the cult of Floyd.

That secret sheds light on one of beer’s biggest, most enduring trends: the rise of “extreme” beers such as tongue-numbingly hoppy imperial India pale ales and Valvoline-look-alike imperial stouts.

Anderson — big, bearded and heavily tattooed — drove me to the brewery and brew pub. On the stereo, he played the Grammy-winning singer-songwriter Gillian Welch. “If that disappoints some beer consumer that I don’t listen to Slayer all day and all night, well, sorry,” he said.

His unexpected taste in music isn’t the only way Three Floyds defies expectations. For one thing, even its milder styles are unusually hoppy. The brewery’s flagship beer, Alpha King, is about as full-flavored and citrusy a pale ale as one can find. What’s more, these beers are scarce: Three Floyds distributes in only five states.

Then there’s the popularity of its Dark Lord imperial stout, a beer so beloved that it has its own annual holiday of sorts, Dark Lord Day, during which the entire year’s supply is released at the brewery. (Anderson says that last year Shopify, an e-commerce site used by more than 15,000 stores, crashed within minutes after tickets went on sale.) Another defining characteristic is the carnival-style tattoo-art aesthetic of both the bottles and the brew pub. “People are listening to punk rock, and it looks like a clown threw up in here,” brewery Vice President Barnaby Struve (also big, bearded and tattooed) said when we arrived.

The beers were uniformly excellent — but the best in the world? They tasted pretty close to similar products from Stone Brewing, AleSmith and any number of other hop-worshippers. So what’s going on?

A persuasive answer comes from Eric Clemons, a professor at the University of Pennsylvania’s Wharton School and an expert on how access to information has transformed the practice of business.

In 2006, Clemons and two co-authors published a journal article about RateBeer that examined how ratings predict sales growth. Beer, Clemons notes, is a highly “differentiable” product: Unlike, say, vodka, it can vary almost infinitely in characteristics from color to alcohol content to flavor and aroma. By analyzing hundreds of thousands of beer reviews, Clemons found that the brewers whose sales grew the most were not just those with high ratings, but those with the biggest gaps between their highest and lowest ratings.

“It is more important to have some customers who love you than a huge number of customers who merely like you,” the paper concludes — even if your beers are so intense that they turn off a lot of potential customers. “Good, solid, likable, average, middle-of-the-range new products that consumers neither love nor hate will not sell.”

Beers that stand out are thus the most successful, and that might be what has led to the proliferation of extreme brews and the supremacy of Three Floyds.

The brewery’s popularity, Clemons told me, hinges on several factors: quality, scarcity, unusual packaging and the outsize reputation of Dark Lord, a “halo brand” that boosts overall prestige. But one factor trumps the others: “They picked styles that America truly loved, and they made them extreme but not too extreme.”

It’s possible, Clemons notes, to make a beer so edgy that nobody likes it. The key is to be as different as possible without being just plain weird.

Three Floyds doesn’t usually use odd ingredients, Clemons added; it doesn’t use funky wild yeast. He contrasted that approach with the experimental one-off beers sometimes brewed by Dogfish Head Brewery’s Sam Calagione.

“Sam is extreme in a way that people have trouble getting their arms around; like, Sam might have a beer that’s organic blue corn pre-chewed by professional corn chewers,” he said. “Three Floyds is extreme in a way that’s centrist.”

The secret to being the best brewery in the world? Be the big, bearded, tattooed guy — but listen to chart-topping albums, not just heavy metal.

Fromson is a former associate editor at the Atlantic. He can be reached through his Web site, www.danielfromson.com.