There are a series of books, called the Elemental Encyclopedias. They are very big and quite pricey, but I feel they are really good books to have. I do not own any of them, but I have spent long hours in the book store reading over them. Here is a list of all the books that are on my wish list. (EE stands for elemental encyclopedia)
EE of Witchcraft
EE of 5000 spells
EE of Magical Creatures
EE of Spirits
These books have a lot of interesting infromation for doing spells and rituals, and I just think they would be a really fun read.