The short stories will be released as e-books on 6 September.
The last Potter release, the script for Harry Potter and the Cursed Child, is already the fastest-selling UK book this decade.
That was penned by the playwright, Jack Thorne based on an original new story by Thorne, JK Rowling and John Tiffany.
The collections of "Short Stories from Hogwarts" are called Of Power, Politics and Pesky Poltergeists, there's also Of Heroism, Hardship and Dangerous Hobbies and lastly Hogwarts: An Incomplete and Unreliable Guide.
Most of the stories have already been published on the Pottermore website.
If you're expecting JK Rowling's usual length you'll be disappointed.
Harry Potter and the Goblet of Fire is 640 pages. The longest of these e-books is 79 pages.
What they're about
One of the collections will "profile two of the Harry Potter stories' most courageous and iconic characters: Minerva McGonagall and Remus Lupin".
It will also look "behind the closed curtains of Sybill Trelawney's life".
The guide to Hogwarts will look more at the "permanent residents" and "discover secrets of the castle".
The third will look at the "darker side of the wizarding world", featuring the "ruthless roots of Professor Umbridge, the lowdown on the Ministers for Magic and the history of the wizarding prison Azkaban".
It will also look again at Tom Riddle, and when Horace Slughorn taught Potions.