So, I was playing around a bit and ran into the question of whether it was water or ice.. and then I began to wonder .
I had chosen water and air as my elemental books. Did that combo give me ice magic? If so, that would be cool..
Books Required = Access to Spells
Water + Air = Ice
Water + Fire = Steam
Water + Earth = Mud?
Earth + Fire = Magma
Earth + Fire + Air = Obsidian
X_Element + Summoning = X_Elemental at L5
2X_Element + Summoning = More powerful critter at ~L8
I'd expect each element to have it's own strong 'flavor', such as Air having baseline spells like teleport and protection from range attack, but if you add earth, you can then learn spells like casting Sandstorm in the forest ..