i have many books of magic, for example tome of cure poison.and now. what is their use?

help me .
thanks

If one of your characters has the correct circle of magic and doesn't yet have that spell, invoking the book from that character's inventory screen will grant them that spell permenantly provided he has enough training in that circle of magic. (i.e. Having a priest invoke the 'Tome of Cure Poison' will write that spell to his spell book since it's a Vine spell which all priests have access to.)