I don't think there is a guide out there to get all spells. You can sort of piece it together if you check the walkthrough and CTRL+F for "spell", probably, but that might also spoil things, I'd imagine.
I don't remember if I added silence protection or not, but silence is uncommon overall, so don't worry too much about it.
If you mean the "Lightning Storm" spell, you get the book as a reward for one of the mages guild quests. If you are a member already, talk to the lady sitting at the library (same room as Alpharius) and she'll offer you the quest (Under The Moonlight).
You can find more details about the quest in the walkthrough,
but do let me know if something has you stumped.
