"Harry Potter and the Prisoner of Azkaban" is the third book in the popular Harry Potter series by J.K. Rowling. In this book, Harry returns to Hogwarts School of Witchcraft and Wizardry for his third year, but he's in danger as Sirius Black, a convicted murderer, has escaped from Azkaban prison and is believed to be coming after him.

As Harry returns to Hogwarts, he finds that the school is guarded by Dementors, dark creatures who feed on happy memories and can cause those around them to relive their worst experiences. Harry, Ron, and Hermione must work together to figure out how to protect themselves from the Dementors and uncover the truth about Sirius Black's escape.

The story is full of twists and turns as Harry, Ron, and Hermione use their skills and knowledge to unravel the mystery of Sirius Black's past and his intentions. They also learn more about Harry's family history and how it's connected to Voldemort, the Dark Lord who wants to kill Harry.

Along with the exciting plot, the book also explores important themes such as friendship, loyalty, and the power of good versus evil. Harry, Ron, and Hermione's friendship is put to the test as they face dangerous situations, but their loyalty to each other never wavers. The book also shows how the characters must make choices between what is right and what is easy, and how those choices can have far-reaching consequences.

The book introduces new characters, including Professor Lupin, the new Defense Against the Dark Arts teacher, and the mysterious Divination teacher, Professor Trelawney. The characters are well-developed and add depth to the story, with their own unique personalities and backstories.

Overall, "Harry Potter and the Prisoner of Azkaban" is a thrilling and captivating addition to the Harry Potter series. It's a must-read for fans of the series and anyone who enjoys a well-written, magical adventure.