Battle Book (Pathfinder Equipment)
From D&D Wiki
Wizards often use this weapon which doubles as a spellbook. The tome is larger than normal (though it holds no more than a common spellbook) and heavy, wrapped in toughened leathers and brass bindings and supports. It can be used as a bludgeoning weapon, balanced just right to be swung around like a club. Likewise it can be enchanted as a weapon. It has enough metal in it to count as the damaging part of the weapon, and can have adamantine and the like added to it.