The Weight of Rubies
All users of magic are spontaneous spell-casters: Anyone can cast whatever spells are available at an appropriate level, without having to prepare it or pray for it the night before. Spellbooks are not required for wizards; however, to learn new spells, a wizard must either have written instructions, or be taught the spell by another wizard.
The basic premise of magic-working is that the spellcaster upon draws upon the magical energies of the world around him, and uses his own will to weave those energies into a spell. A spellcaster can see these energies around him, and can even see the energies of others’ life force.