Need a Mage, a rogue and a monk and also have a strange key

In the library there is a locked room

Rogue - unlock east to open Monk - enter room and do what you need to in there, also strange key is here if needed Mage - push Bookcase to open a passage west 1n of locked room

Once monk is finished a way west appears again

Once at the tome

turn strange key twice

ex case

Get tome

ex switch