Found in the basemant of Benirus Manor. Verrrrr mysterious.
The Tome of Unlife. http://www.uesp.net/wiki/Oblivion:Tome_of_Unlife
According to the wiki, it says in Daedric "The First" and "The Last".
Is there nothing else in the game to do with it? The Lore section has nothing on it either. It belonged to the evil dead guy. Lorgren Benirus.
Just cheesing around. Thought I'd see if anyone had any ideas.