The Masks of God
by Joseph Campell

There are several books in this series, each of which took years to research, making Campbell the best candidate for High Priest of Polytheism.

The Masks of God: Primitive Mythology
The Masks of God: Oriental Mythology
The Masks of God: Occidental Mythology
The Masks of God: Creative Mythology

These books are probably the best antidote for anyone who grew up believing the myths s/he were raised on were the only ones that got it right.