While there's certainly debate about spirits and the supernatural here in our world, in the fantasy realms we so often find ourselves when we play RPGs, there's no question about it: they're there. Endless Realms: Tome of Spirits looks to help be the ultimate guide to all things spiritual in your games. The book is up on Kickstarter now.
From the campaign:
The campaign's about 5/6 of the way to their goal with still 22 days to go.