The Book of law is a book held in place of a shield, and is the God book aligned with Armadyl. It can be purchased from Jossik for 5,000 coins after completing Horror from the Deep. Books of law must be made using all four torn Armadyl pages which can be purchased from other players, or obtained from Treasure Trails.
Equipping a book of law allows the player to preach and perform ceremonies, such as blessing, last rites, and wedding rites, by operating it (none of which have any effect on the game itself, and are simply recited lines of text), costing 25% of the player’s special attack energy.
Lost books of law can be reclaimed by speaking to Jossik, complete with all pages that have been added, for no cost. Alternatively, for those who do not wish to travel to the Lighthouse, Perdu will return them to players for 12,000 coins.
The completed book has the fourth highest ranged bonus of all off-hand items, following just behind the odium ward.
The Book of Law DOES count as an Armadyl item for God Wars Dungeon.
Filling the Book of law currently costs 1,060,565 coins when buying each page individually or 1,133,065 when buying the item set.