A fourth book for the MLP Princess Collection has appeared over on Hachette Books website! Called "Twilight Sparkles and the Forgotten Books of Autumn" it's obvious that it'll star Twilight, but the page gives little in the ways of information other than that tidbit other than the release date which is November 1st, 2016.
Furthermore, it appears that a boxed set will also be available starting November 1st as well so if you haven't jumped into the books yet you can get them all in a convenient package.
Thanks to Jason and Brony250 for sending it in!
Source
Box Set
Twitter: Calpain
