Kinda. You have a spell book, and from there you have several memorised spells, and from thoes; you can cast them untill you are blue in the face, or untill you run out of spell points.
Sorcers have a more limited selection of spells, but can cast any of them at any time (untill they run out of spellpoints)
No changing spells between missions for the sorcerers though... they just got what they've got, and are stuck with it.
priests are like mages, they have to 'prepare' a select numbe rof spells from a list of pretty much every spell ever. from there, they can cast them untill they run out of spellpoints.
pretty ballanced really.
-RuskiFace the Pirate