You need to complete the Tomes of Magic sidequest, which can be started in Ulcaster School. The ghost of Ulcaster will walk around the school ruins at night, talk to him a few times to start the quest.
To finish the quest, fight through the Ulcaster School dungeon, until you find a pile of bodies that you can loot for the "Ulcaster's Dusty History" book. Return it to the ghost of Ulcaster to unlock the achievement.