If you move the mouse cursor over the mc's icon, the task appears:
- I wonder if there's anything useful in my bedroom.
as pending, it starts selecting the books on the top shelf, then the middle shelf, then the bottom shelf, then the top shelf, then the middle shelf, and continues selecting them in a loop until the message appears that the mc has found the book of Sin that is hidden there. No idea why it is necessary to select them several times in loop starting with the books of some shelf, but it also happened to me that selecting the books of the three shelves only once, the mc didn't find anything, and that task (- I wonder if there's anything useful in my bedroom.) continued as pending, until in the same search after repeating it in loop selecting the same books a couple of times that Book of Sin Vol. II appeared.