To start the quest you can talk to Amber and tell her about quest (it's not needed) and she will tell you that she lost her notebook. The notebook is located in the east part of Rookgard. To get there you have to get past the brigde and then walk like this map show (you will have to kill different Rookgard creatures like Spiders, Wolves, Bugs and Poison Spiders):
Close to the chests you will have to kill creatures like Spiders, Bugs and Poison Spiders. Open the chest here and you will find a book:
Now get to Amber below the Rookgaard library (at the sleeping room) and talk to her like this:
Hi, Notebook, Yes
You will receive a short sword now!