Part of Settlers' success can be attributed to its well-designed gameplay. Adam Weisberg, a finalist in the 2006 Settlers of Catan US Championship, notes that the game "is easy to learn because it draws on equal parts strategy, gamesmanship and luck." The rules give you enough choices to keep it interesting, without so many as to make it overwhelming. As a result, says Weisberg, "with a little luck, a sharp new player always has a chance to beat an expert."
Invented by German designer Klaus Teuber in the mid-1990s, Settlers of Catan involves three or four players building settlements, trading resources, and racing to earn 10 victory points. Each game begins with a shuffling of the board tiles, producing a wholly different board each time. Settlers allows players to produce resources, build roads and settlements, buy "development cards," and trade with one another.
Where games like Monopoly fall short—with playing times that far outlast the players' interest, particularly those who have little hope of victory—Settlers is designed to maintain close competition. Unlike games of Risk that can famously last for days, Settlers usually takes 90 minutes or less. And unlike many pastimes that quickly descend into cutthroat competitiveness, Settlers of Catan is not a zero-sum game. A single roll generally produces resources for multiple players, and trades are almost always mutually beneficial. Because Settlers is a unique game that rewards cooperation as much (if not more) as confrontation, Weisberg argues that it "brings out competitive spirits in a positive way."

Bergen Offentlige Bibliotek/flickr
Still, plenty of well-designed games remain mired in obscurity. There are a number of theories explaining how Settlers expanded out of the geek basement to corporate breakrooms and household living rooms. Blake Eskin argued in the Washington Post, for instance, that Settlers has taken hold because it exemplifies many aspects of our modern world, such as limited resources and intertwined global economies.
Another way to view the mainstreaming of Settlers is part of the larger trend of "nerd culture" slowly infusing into "popular culture." For example, while X-Men and Green Lantern were once idolized by just a sliver of society, now millions go watch them at movie theaters in a seemingly endless parade of superhero movies.
Settlers is taking a similar path to popularity. Not long after its inception 16 years ago, Settlers found a welcome home among gamers. "The nerds recognized it first" argues Charlie Cromer, a nerd culture enthusiast who's been attending gaming conventions for the past decade. "They were the ones willing to take a chance on an obscure foreign board game." In the case of Settlers, nerds were the early adopters that Malcolm Gladwell discussed in his book The Tipping Point, a necessary component for a product to take off.