Quidditch Through the Ages to Find Them" have raised £17 million. In 2001, Rowling penned two companion books to the "Harry Potter series", "Quidditch Through the Ages" and "Fantastic Beasts and Where to Find Them", for British charity and offshoot of Live Aid, Comic Relief with all of her royalties going to the charity. As of July 2008, the books combined are estimated to have earned over $30 million for Comic Relief. The two books have since been made available in hardcover. Within the fictional world of "Harry Potter", "Quidditch Through the Ages" is written by Kennilworthy Whisp, a renowned Quidditch expert. In both
The Magical Worlds of Harry Potter approval from Rowling, and has since received positive reviews from critics. An updated version of "The Magical Worlds of Harry Potter" was published in 2004 by Berkley Books. "The Magical Worlds of Harry Potter" explores the references to history, legends, and literature in J.K. Rowling's "Harry Potter" novels. David Colbert, the author of the book, told the "St. Louis Post-Dispatch" that the "Harry Potter" novels "are [...] literary treasure hunts for [Rowling's] readers. What seem like funny-sounding names and places and excursions into fantasy all have a basis in either history, myth or legend." He added, however, that he thinks