The book, Harry Potter and the prisoner of Azkaban, is written by J. It's the third book of the well-known Harry Potter series. Azkaban is a prison in the wizard world. The main problem in this book is that a feared mass murderer escapes out of the prison and that explains the title.
Harry Potter is a wizard. He goes to the Hogwarts School for Witchcraft and Wizardry, and this school year will be his third year on Hogwarts. In the summer holidays he lives with the Dursleys, a Muggle family. Muggle is the wizard word used for non-magic people. Harry can't stand the Dursleys and neither can they stand him. This is because the Dursleys hate all things that have to do with magic, including Harry. For several years they had pretended that Harry's parents were killed by a car crash. But actually they were killed by the most feared Dark wizard for a hundred years, Lord Voldemort. Harry, who was then only a baby, had escaped from the same attack with nothing more than a lightning shaped scar on his forehead. Because instead of killing Harry, the curse rebounded on Voldemort himself. Barely alive, Voldemort had fled to never return until Harry's first year on Hogwarts. But also that time Harry managed to escape.
During the summer holidays everything seems to go as usual. Until he gets a terrible quarrel with the Dursleys, because he accidentally put a spell on an aunt when she made him really angry. Harry runs away from the Dursleys and is picked up by a bus for wizards. He goes to London where he always gets his school equipment and stays there the last weeks of the holiday. At the end of the holiday he meets his friends, Ron Weasley and Hermione Granger. Together they go by train to Hogwarts, but before leaving Harry hears that Sirius Black, one of Lord Voldemort's followers, has escaped from Azkaban. Black landed in prison because he had killed about a dozen people in one blast, including a wizard called Peter Pettigrew.