From Ars Magica
Spell Books can be used to store spells and spell recipes, thus freeing up inventory space. The GUI, when opened, consists of two pages. The left is for active spells, and they can be cycled through using the 'z' and 'x' keys. They will appear in the in-game GUI when the spell book is equipped.
The right page is just for storage. Spells there cannot be cycled through. The right page also accepts spell recipes.
Spell books can be colored. All colors are supported except for light gray, magenta, pink and lime.
Spell books can be named if used in an anvil and the appropriate amount of xp levels spent.
Colors do not affect the functionality of the spell book; they are simply there for organizational purposes.
Holding Shift and right clicking will open up the Spell Book displaying the GUI below. The left side is for active spells that will show up when the book is your active slot and the right side is for storing other spells and spell recipes.
Max Stack Size