Bungaku Shoujo Memoire consists of 3 24-minutes episodes each dedicated to one of the girls protagonists of the movie, giving us a backstory.
The first one is dedicated to Tooko. It narrates what happens before Konoha sees her eating a page from a book under a tree at school - which is exactly when the movie starts. The protagonist of the second episode is Miu, while the third one focuses on Nanase.
The three episodes expand on the storyline of the movie, giving additional depth to the three characters, but maintaining the style, atmosphere and feeling of the movie. It's pervaded by a gentle, warm feeling. The animation and visuals are lovely and so is the soundtrack.
If you liked Bungaku Shoujo the movie, I'm sure you will appreciate Bungaku Shoujo Memoire too.