Religion
GURPS Religion is a fairly comprehensive treatment of using religion in a roleplaying game. The presentation of the material favors the worldbuilder or GM who wants to create new religions and deities for his world¸ but there is reference to real world religions¸ and the book will still be of (lesser) use for GMs who wish to use religions from history or fiction in their games.
The Universe. Some Assembly Required. So you want to dance with the gods. You want a priest who can call down bolts of power from the skies. You want to cure the diseased and dying¸ and you want hordes of fanatic followers to bow to your every command. What you need is GURPS Religion. GURPS Religion gives you everything you need to delve into the mysteries of creation and divine power. It opens up whole new vistas of roleplaying. Recreate gods from fantasy and myth¸ or create your own pantheon and answer the cosmic questions... Who created the universe¸ and why? Is there one deity or many? Are the deities wise and benevolent¸ or are they rash and vengeful? How do the characters get divine power? GURPS Religion allows you to design a complete cosmos. It also helps you decide what part (if any) the gods play in characters' day-to-day lives¸ and how to create the social institution we know as religions. There are also sections on designing clerical characters¸ and rules for the magical powers granted to the faithful. Power¸ magic¸ birth¸ death¸ and intrigue. The world of the gods is vast and complex. You can be a pawn of the Powers That Be. Or you can make the universe bend to your will. You have the knowledge. You have the power. Create the Universe!