If you've ever found yourself muttering "I need sheep!" while hanging out with friends, you will probably enjoy reading the backstory of Settlers of Catan.

18 million copies sold worldwide at $42 apiece plus merchandising makes it the most successful board game ever:

Paraphernalia in the online Catan shop includes socks and custom-designed tables. Rebecca Gablé, a German historical-fiction author, has written a Viking-era Settlers of Catan novel. Pete Fenlon, the C.E.O. of Mayfair Games, said, “Our volume of sales will be such that, over time, Catan could, in terms of gross revenue, be the biggest game brand in the world.”