Some of you may not know how to actually launch the Justine DLC, which is understandable as it's neatly tucked away. Here's the simple walkthrough with pictures.

Head to your library and play Amnesia The Dark Descent.



Next, click "Run settings launcher"



Finally, select the Justine button at the bottom right of the window.

The achievement is earned once you reach the Library area. It looks like this:



Go forward and into the room with the projector.



Turn right and head to the bookcase facing you.



Search the shelves for a book you can move. Then pull it away.



The note will be behind the book. Pick it up and read it.





Achievement unlocked.