When you're picking up the books on your-back-to-school list, don't forget the most important ones: J.K. Rowling's three "Harry Potter" short story collections. Announced today on Pottermore, the collections will arrive just in time for your trip on the Hogwarts Express this September.

The three eBooks -- which fall under the "Pottermore Presents" name -- will collect information from Pottermore's archives; that is, original writing by Rowling herself. There will be three collections total: "Hogwarts: An Incomplete and Unreliable Guide," "Short Stories from Hogwarts of Power, Political and Pesky Poltergeists" and "Short Stories from Hogwarts of Heroism, Hardship and Dangerous Hobbies."

According to the books' official descriptions,

"Hogwarts: An Incomplete and Unreliable Guide" dives into the nooks and crannies of the beloved wizarding school itself, unfurling everything from details about the Hogwarts ghosts, to what happens when the Sorting Hat can’t decide on a student’s house.

"Short Stories from Hogwarts of Power, Political and Pesky Poltergeists" explores the darker roots of the wizarding world. You’ll learn more about the troubles that faced the Ministry of Magic, the horrors of Azkaban prison and enjoy an entirely new original piece of writing by J.K. Rowling on Horace Slughorn.

Finally, in "Short Stories from Hogwarts of Heroism, Hardship and Dangerous Hobbies," Pottermore celebrates the colourful staff of Hogwarts. There’s more to discover about Care of Magical Creatures teacher Silvanus Kettleburn, as well as another new piece of writing from J.K. Rowling on Minerva McGonagall, and her involvement in the second wizarding war.

The "Pottermore Presents" series is currently available for pre-order across on Pottermore as well as a variety of digital platforms, including Barnes & Noble, Amazon, iBooks and Kobo Books. Priced at $2.99 each, the three new collections officially go on sale September 6.