Chronicles of Iridia
I encourage the use of most books that are available as long as the player has a justifiable reason as to why the character would have the ability and if the ability fits in the overall restricted magic world they live in.
This being said, I have a heavy hand in determining the availability of certain classes, spells, and equipment allowed during the course of the game. This is an epic fantasy, I want the players to earn their powers and grow with their characters instead of just getting that awesome +28,000,000 Flaming Burst Long Sword, or abusing the system to create an Über character that destroys everything the GM throws at it. I consider this story to be Fantastical Realism, and the plot and characters should reflect this as well.