I'm exploring the 1st level and I'm stumped by the bells. There's supposed to be a letter that provides part of the solution, in the small room off a larger room, it appears to be some sort of small library or study. However I am unable to find the hidden items even though my party is in stealth mode.

I'm not sure what I'm doing wrong here.

Edited September 11, 20196 yr by Hayashi.226

There are several ways to open the door:

1. 10 mechanics: lockpicking
2. 5 mechanics: find the key hidden in a book on that floor
3. Ring the bells. The correct sequence is: 

right, middle, left, right

You can find out the sequence if you interact with the spirits that you can find on that floor. They appear once you clear the enemies in the corresponding rooms.

Thank you. Is there like a minimum perception or some other stat in order for hidden items to be revealed?

No Perception isnt used for finding hidden objects (In POE2 it is). Mechanics skill is used for finding hidden object and lockpicking and trap disarming 

Edited September 11, 20196 yr by draego

Yes, it's mechanics. As I wrote above 5 mechanics (on anybody in the party, doesn't matter who it is) is needed to find the key hidden in a book (on a table). Scouting (aka sneaking) will give you a bonus when it's about searching for hidden thngs and traps. So make sure you bring somebody who maxes mechanics and scout/sneak everywhere where you haven't been before. 

Thank you guys. This game has a rather steep learning curve...