Harry Potter and the Prisoner of Azkaban by J. K. Rowling

Harry Potter and the Prisoner of Azkaban is the third novel in the Harry Potter series written by J. K. Rowling. The book was published on 8 July 1999. The novel Harry Potter and the Prisoner of Azkaban won the 1999 Whitbread Book Award, the Bram Stoker Award, the 2000 Locus Award, and was short-listed for other awards, including the Hugo. This placed the novel Harry Potter and the Prisoner of Azkaban among the most-honoured works of fantasy in recent history.
Harry Potter and his friends Ron Weasley and Hermione Granger return to Hogwarts School of Witchcraft and Wizardry and find security has been tightened because of Sirius Black's escape. The grounds are now guarded by Dementors, dark, sinister beings that drain the happiness of anyone nearby and guard Azkaban prison. They also cause Harry to hear his parents. Professor Remus Lupin, the school's new Defence Against the Dark Arts teacher, tells Harry Potter he is more vulnerable to the Dementors because he has seen genuine horrors in his past. He agrees to teach Harry Potter the Patronus Charm, a shield against the Dementors.
Harry Potter is depressed to learn he will not be allowed to visit Hogsmeade, the local village, because Uncle Vernon refused to sign Harry Potter's form. He is also angry with Draco Malfoy for ruining Hagrid's first lesson as Care of Magical Creatures teacher. Malfoy causes himself to be attacked by Buckbeak, Hagrid's beloved Hippogriff, and his father ensures that Buckbeak is sentenced to be executed in the course of the year ... (Summary by Wikipedia)