Harry Potter is back for a third year at Hogwarts School of Witchcraft and Wizardry, along with his best friends Ron Weasley and the ever-studious Hermione Granger. Before he returns, however, he has to endure another summer with the dreadful Muggles (non-magic) family, the Dursleys: Uncle Vernon, Aunt Petunia and Dudley. To add to the tension, the news is all about an escaped murderer, whereabouts unknown, and Aunt Marge is coming for a visit. Harry doesn't know which is worse. Eventually, the situation blows up, and Harry is certain he'll be expelled for using magic while outside of the school. He heads for London, courtesy of the Knight Bus, a wizardly mode of transportation, intent on getting enough money to try to live on his own.

When he is greeted at Diagon Alley by the Minister of Magic himself and told all is forgiven, he is both relieved and wary. He learns that the escaped murderer was no ordinary person; rather it is Sirius Black, a powerful wizard imprisoned for twelve years in Azkaban. Harry knows little about the terrible wizards' prison, but he does know it is a place he wouldn't want to visit in a hurry.

When the Weasleys arrive, Harry learns that Sirius Black may be headed for Hogwarts -- and Harry. It seems that Black was the person who betrayed Harry's parents to Voldemort, which resulted in their deaths. As a result, Harry and Hogwarts are under fairly strict surveillance. Furthermore, Azkaban has sent its own guards to watch the school -- eerie, cloaked creatures called dementors who have a particularly powerful effect on Harry.

Apart from the threat on his life, Harry is soon immersed in his third year at Hogwarts. Hermione seems to have taken on a staggering workload, and Draco Malfoy is up to no good as usual, but Harry still has Ron and Neville Longbottom and his slot as the Seeker for his Quidditch team. Potions teacher Severus Snape is as spiteful as ever and Professor Trelawney, the divination instructor, is downright weird, but these points are outweighed by the new Defense Against the Dark Arts master, Professor Remus Lupin, who seems to genuinely admire and respect Harry

It soon becomes clear that Sirius Black is indeed in the vicinity of Hogwarts, and Harry and his friends are drawn into the mystery and the suspense, almost at the cost of their lives.

As in the other two Harry Potter books, the pace never flags, and the book is almost impossible to put down as the plot twists and turns, always staying one step ahead of the reader. It appeals to a very wide range of readers, seeming to almost magically "fit" whomever is reading it. Harry is a winning character with whom just about anyone can identify, and his friends are the kind of people anyone would want to know. Professor Lupin is a particularly appealing and well drawn character, but in this book, Snape goes a little too much over the top. It is hard to imagine a headmaster like Dumbledore could be blind to or tolerate Snape's nasty and capricious behavior, and it makes me wonder just what is going to happen in future books. (Perhaps that's the idea.)

I'm already looking forward to Harry's fourth year -- and I hope it's soon!