This mod adds spell book items (of weapon type) that give abilities to the unit to cast new spells that are not in the Arcane spell books.
There is :
-40 spell book items, 1 staff and 1 armor that unlock a total of 93 new spell abilities;
-4 new unit stats: Fire Mastery / Water Mastery / Air Mastery / Earth Mastery. Which increase the proficiency of each ability elements (they are upgradeable, just scroll down the stats in the level up screen);
-10 new potion/infusion items for Mana and Essence;
-10 new ring items that increase Int, Ess and elemental mastery;
-5 mage robe items (surcoat);
-52 new technologies that unlock the new items;
-6 new factions: Kingdom of Mage, Kingdom of Mage II, Empire of Wizard, Empire of Wizard II, Magic Kingdom Of Capitar and Magic Empire of Kraxis.
Mage and Wizard have a striped down version of Kingdom and Empire tech tree (I removed weapon and armor tech) plus the new Technologies.
Mage II and Wizard II are just copies of Mage and Wizard so you can have more opponents.
The Capitar and Kraxis are duplicates of the Faction with the same name but with the 52 new technologies
-1 new improvement, Crystal Maker for Mage and Wizard faction only.
The spell books are divided in 3 main tech branches:
Black magic: These are Fire/Water/Air/Earth elemental spells that are focused on dealing damage;
White magic: These are focused on healing and buffing spells;
Mathematics: These are somewhat wacky spells. Don't take it too seriously. 
Also, remember that I made this mod for fun in my spare time. It is not balanced nor polished yet and might have bugs or typos in it. I will spend more time on it depending on the success/popularity it gets.
Known issues:
-The AI has a little trouble with the new items when designing units. I had to create predefined units with the right combination of items so the AI would train coherent units. But it still struggle a little. I'm not sure what I should do to improve this.
-The books items do not unlock any physical attack type but still boost the Attack stats. I used the Attack stat as a way to fool the AI into thinking the spell book items are good for combat by affecting the combat rating of the unit. Again, I'm not sure it's the best solution.
To install it, just unzip the file in your Elemental folder, probably something that look like: C:\Users\YourUserName\Documents\My Games\Elemental\
Download
Enjoy!