The fourth book in the Harry Potter series is titled "Harry Potter and the Goblet of Fire." It was written by British author J.K. Rowling and published in July 2000. The book follows Harry's fourth year at Hogwarts School of Witchcraft and Wizardry, during which he participates in the Triwizard Tournament, a magical competition between three schools of magic. The book is notable for being significantly longer and darker in tone than the previous books in the series and includes the introduction of several important characters, such as Cedric Diggory and Mad-Eye Moody.