Books of Knowledge are Wealth that you can find in any region of Norway or England in Assassin's Creed Valhalla. They represent the various skills that Eivor can use to fight. There are two categories: melee and sitance.
These skills can be an aid in concealing your character for assassinations or, if you prefer, a way to deal heavy damage like a beast. You'll be able to equip four skills of each category, so you'll have to make a choice.
Note that it's possible to increase the level of your ability by learning a similar book of knowledge.
Books of Knowledge in Essex
First ability and its location
• Rank 1: Use your raven, Synin, to briefly distract your enemies.
• Rank 2: Synin attacks the target to being the distraction. During combat, Synin Stuns the target.
Second ability and its location
• Rank 1: Impale an enemy with your harpoon and throw them in any direction. Enemies who strike objects or other enemies will suffer massive damage
• Rank 2: Eivor can finish by pulling the enemy close and killing them with style!
Original content by Camille"Effylia" Bouin.
Books of Knowledge are what allow you to gain new abilities in Assassin's Creed Valhalla. Part of Wealth, it's often very easy to find them in the Cent region if you want to increase Eivor's strength.