The most comprehensive pantheon in roleplaying games is back in a new edition for 5E. This massive tomes provides more than 20 pick-up-and-play churches, whose organization and beliefs are described in lavish detail. These churches can be used in any campaign setting to bring a whole new level of detail to the religious characters. Plus, for those who don't have a complete cosmology in their game, The Book of the Righteous provides a comprehensive mythology that unifies all of the gods in the book. The original edition of Book of the Righteous was one of the most critically acclaimed books of the d20 era. Now Dungeons & Dragons Fifth Edition designers Robert J. Schwalb and Rodney Thompson have brought the new edition up to date with the 5E rules.
If you want to homebrew a setting for Dungeons and Dragons' 5th edition, this is a good resource! A good, solid foundation for a panteon if you want a pre-written one, a lot of info on how to adjust the panteon to your particular setting, and info on how to make your own gods and mythology from scratch. Combined with a number of fun sub-classes and new spells (naturally focused on divine matters) this is a worthwhile addition to your D&D book collection, should you have one of those.
The only downside is that this book is rather dense, text-wise. I've got poor eyesight and limited free time, so getting through this all took a good while.