afraid thats west. well, northwest - can get to it from both. easier from north.
firstly, get yourself a key from doing a quest in east - you get the quest from a pavilion thing in eastern feralas.
use that key to let yourself into north.
now, i'm not sure what class you are, but the next thing to do is wait for the patrol to move out the way, and then dash to the ramp in front of you, jump onto the banister on the left of the ramp, and then onto the ledge below you. run round this ledge round to the west, and theres a door recessed into the ground. jump down to it. open the door with your key. run along the corridor, and you come to the library. talk to the bloke, get your trinket