Abbots Prayer Book is obtained by killing the Demon Hezwerd found in the Lauke Monestary in Vena.
The book normally drops when he is killed. The book is considered to be a Healer or Mage class item. Since the Prayer book is a blue named item, it cannot be traded in-game. It can only be traded through the exchange market. It is highly recommended any party's killing the Hezwerd to set the party's distribution to "Free" and have any healers or mages obtain the item.