A mage's book is a book in the shield slot, requiring 60 Magic to wield. It is tied with the ancient wyvern shield for the third-best Magic attack bonus in the shield slot, behind the arcane spirit shield and the Elidinis' ward (f), but it has no Melee or Ranged defensive bonuses. The mage's book is popular among combat pures because there is no required Defence level.
It can be obtained from the Mage Arena shop with mage arena points. Points are obtained by killing amges in the actual arena.