Today Pottermore users can begin exploring the first chapters of Harry Potter and the Prisoner of Azkaban.  The Insider has been updated with the following information:

Board the Knight Bus, enlist the help of Sir Cadogan, attend a Defence Against the Dark Arts lesson, and much more.

There are also five new exclusive content entries from J.K. Rowling to discover, including additional information on Aunt Marge.

Remember that you need to progress through Harry Potter and the Chamber of Secrets on Pottermore.com before you can explore Harry Potter and the Prisoner of Azkaban. You will also need to collect all the items from your second-year shopping list, which can be found in Chapter Four, Moment One of Harry Potter and the Chamber of Secrets.