The History of the Quidditch World Cup is a 2,400 word history of the fictional game Rowling invented for the series. It's played by witches and wizards on flying broomsticks, and is a key plot point in a couple of the novels.
"We’re thrilled to have the opportunity to publish such an imaginative and engaging story from J.K. Rowling about the history of the Wizarding world’s most exciting sport," said Susan L. Jurevics, Chief Executive Officer, Pottermore. "We’re committed to being the only digital destination where fans can discover new original content about the world of Harry Potter from J.K. Rowling. ‘History of the Quidditch World Cup’ helps us not only fulfill that mission, but it also serves to entertain and delight our community."
The History is going to be released in 2 parts. The first section, which was posted today, focuses on historical background about the tournament, information about how the tournament works, and examples of controversial tournaments, including the infamous 1877 match played in Kazakhstan’s Ryn Desert now known as the Tournament that Nobody Remembers. The second section will be published next Friday. It will feature amusing recaps of some notable recent matches that have been held every four years since 1990.
Based on the quotes provided in the press release, it sounds like an amusing read. For example: "The rulebook concerning both on- and off-pitch magic is alleged to stretch to nineteen volumes and to include such rules as ‘no dragon is to be introduced into the stadium for any purpose including, but not limited to, team mascot, coach or cup warmer’ and 'modification of any part of the referee’s body, whether or not he or she has requested such modifications, will lead to a lifetime ban from the tournament and possibly imprisonment.'"