Greater Storms Spellbook. White or Black yes. You'll wait a long time in Deli getting White, but you can get it at any point in the game. Black requires you to kill Lost, which is a somewhat hard point to get to if you don't have good weapons. I would suggest getting Black if you don't want to spend hours to get White, but if you don't have good enough weapons to kill Lost and Democan, get White.