Does anyone know how to get more spells and get a spell book for Supernatural?

Thank you for your help!

As far as I know, there's no spell book in game and you automatically learn new spells as your magical skill rises. The function of the spell book in TS2 was to raise the magic skill and your alignment to either good or evil, but that function in TS3 is filled by the "practice magic " interaction. There is a spell book that comes from the TS3 Store, but it's completely separate from Supernatural and the spells in it are not related to the spells from Supernatural

Gardening Spell Mod

http://modthesims.info/download.php?t=543219

I wish there was more, I might make some once I take up modding.

There's the Store Lady Ravendancer book, which I have but have not used--I think it has nothing to do with Supernatural spells, though. It better not, since I don't have Supernatural.

The Lady Ravendancer book does not require Supernatural, nor do the cauldron or voodoo doll (also from the Store.)
You learn more spells by practising magic and casting spells.

DramaticGamer's Sims 3 Disasters and Blessings mod
http://modthesims.info/download.php?t=521931

If you use the Ravendancer book it wiil raise your magic level and you will get 4 or 5 useful spells. It's a nice compliment to Supernatural. The cauldron might be, but I don't use it.