Which J.K. Rowling book won the 1999 Nestlé Smarties Book Prize in the 9–11 years category?

Harry Potter and the Prisoner of Azkaban won the 1999 Nestlé Smarties Book Prize in the 9–11 years category.

The third Harry Potter novel was published in the United Kingdom in 1999. It introduces Sirius Black, a prisoner who has escaped from Azkaban, and expands the series’ history through the Marauders and their connection to Harry’s parents.

The Nestlé Smarties Book Prize was a major UK children’s-literature award based on votes from child readers. Prisoner of Azkaban won the 9–11 years category in 1999, continuing the early series’ strong performance in children’s-book awards.

The novel also won the 1999 Whitbread Children’s Book Award. It is often regarded as a turning point because the story becomes darker and gives greater attention to Harry’s family history and the moral complexity of the wizarding world.