How can my use the magic books? Do you just use, or? Is it like using a musical instrument? Is it me or some of the book like regular spells?

Right-click on the book in the Inventory screen, and click on the "Invoke" icon.

-Sazerac

silly question, but had to ask...THANKS

NO question is silly here!

And welcome to ye!

-Sazerac

I actually have a related question:

I have never been able to figure out the rhyme or reason to why I can invoke some books and learn the spells and not others.

I think you need to already be adept in that school of magic; however, I have had several books that I have not been able to use although the character trying to invoke it already has access to that school of magic.

Can anyone explain?

I think that you need to be naturally able to learn a book of magic before you can invoke it (i.e. your wizard became a samurai which allows you to continue sun spells but you can't use a book of Lightning because Samurai don't learn stone spells). I'm not sure if this is right but that's my experience.

-Jafin

Yes, you are correct. You can use only those books that belong to the magic school learned by your role:
Paladin - only Spiritcraft
Ranger - only Vinecraft
Warlock - all
Samurai - only Suncraft
Assassin - Mooncraft and Fiendcraft
Barbarian - none
and so on.
On the other hand, you can learn a spell of any school if you level up and have the corresponding skill. If the school belongs to your role then you can learn spells up to level min(your_level,skill_level), if it does not then you can lear spells up to level min(your_level,skill_level/2) where skill_level = Vinecraft, etc.

Also: you can't invoke a spellbook if it's for a spell that's higher than your current level (especially if you've role-changed, even if the spellbook is one supported by the new role).

-Sazerac