The Book of the Fang is on Krokosphinx in Kroktopia. You will have to take the boat to get to Krokosphinx. Once on Krokosphinx find Niles the tree. Once you see him, you will see a ladder to take you down somewhere. Take the ladder and then you will see the Balance School teacher Alharzed. Look to the right of him and there you will see the Book of the Fang. Good Luck on your quests.