Decision achievement, if you unlock this one you can't get "New Look" or "The Richest Girl in the Cemetery" in the same playthrough.
This one takes place when trying to get the Enigmarillion. If Agatha tries to leave the library with a book on her inventory, the librarian will inform her that she needs a library card, she can give us one, but needs a photo of Agatha. For this achievement we're going to come back with a photo.
First, go to the photo booth near the butcher store and use money on it, then pick up the photos.
Come back to the library and give the pictures to the librarian. Easy!