The knowledge book is a type of book that gives you the knowledge of the Crystallized Ancients(coming soon) which lets you know how to enhance your armor with an enhancement table when you right-click it.

Invisible Armor

This knowledge book gives you the knowledge of how to make your armor invisible(not the player itself).

Jump Boost

This knowledge book gives you the knowledge of how to jump higher.

Water-Walking

This knowledge book gives you the knowledge of how to walk on water.

Dragon Wings

This knowledge book gives you the knowledge of how to fly with the Ender Dragon's wings.