J.K. Rowling’s Harry Potter books are among the bestselling books ever written, with half a billion copies sold since the first novel in the series was published in 1997. Since then, the fantasy world the books created—where a wand can clean up your room and school is an exciting place where you fight evil with your friends—has taken on a life of its own, with Harry Potter societies created by students at universities across Britain. Here, Katie Savva, of Warwick University’s Harry Potter and Quidditch Society and captain of its quidditch team, talks us through her group’s favourite Harry Potter books and explains how to play the game without a flying broomstick.