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

When Harry and his best friends go back for their third year at Hogwarts, the atmosphere is tense. There’s an escaped mass-murderer on the loose and the sinister prison guards of Azkaban have been called in to guard the school. Lessons, however, must go on and there are lots of new subjects in third year – Care of Magical Creatures and Divination among others – to take Harry’s mind off things!