This quest is not available in game.
Bring the book Rituals of Power to Tabetha in Dustwallow Marsh.
Hm... now that I think about it, I don't have my book! You see, I had some gambling debts and to pay them off I sold the last copy of Rituals of Power to a member of the clergy....
A member of the Scarlet Brotherhood. He must have taken it to their library in the Scarlet Monastery in Tirisfal Glades!
If you want that book, then you'll have to go to the monastery to find it. And sorry about all the trouble. I'm not myself these days...