Within the fictional world of Harry Potter, Quidditch Through the Ages is written by Kennilworthy Whisp, a renowned Quidditch expert.
The book traces the history of Quidditch, as well as the earliest broom-based games. According to Madam Pince, the copy in the Hogwarts library is "pawed about, dribbled on, and generally maltreated" nearly everyday, which Albus Dumbledore says is a high praise for any book. Harry Potter enjoyed this book. When Severus Snape caught Harry outside the school with this book in Harry Potter and the Philosopher's Stone, he invented the rule that no library books were allowed outside the school, and took it. When Harry came to get it back, he caught Snape with Filch, and discovered Snape had been bitten by Fluffy. Harry didn't get the book back, and it hasn't been seen since.
The real book was written by J. K. Rowling, although Kennilworthy Whisp's name appears on the cover, with proceeds going to the charity Comic Relief (ISBN 0-7475-5471-4)The fictional book
The real book