When you come to the castle study, the paper in the study will know the way to re-enter. Paper content: Pick up the red wine glass (in the task, Prince Of Czech picks up the red wine glass and enters the twisted bookcase) and the red cloth three times (this is the way to re-enter).

In other words, click on the red cloth on the right side of the door and click three times.

Click three times and a rope will appear. Click on the rope.

The bookcase will open, click to enter the twisted bookcase.