It is unclear how some spells are different or what they do exactly.  The spellbook description should make this very clear.  What is the difference between fireball and firebolt for instance, they have the same description and cost the same?  Should tell us damage potential, range (if applicable), etc.  Another example is protect.  Description tells us that it protects against spells.  To what degree does it protect though?  Is the unit now immune to spells or is there a chance spells targeting him will fail?