Reddit mentions of The Book of Gods & Goddesses: A Visual Directory of Ancient and Modern Deities

There are plenty of books on Gods and Goddesses with basic descriptions like this one, but I'm not sure of any from the perspective of occultism and invocation. I have to imagine there are though.

My understanding comes from teachers, study, and experience. Experience is the best teacher though as many mythological depictions miss the point or are difficult to understand. Like Aphrodite being a cheater, sure that's how her energy may manifest sometimes, she is pure attraction, but that's more an abuse of her power than it is her will. She is true divinity, pure and blameless at the highest level.

For study, I'd recommend astrology, or at least exploring the zodiac and planets. If you understand the elemental, zodiacal, and planetary energies, it's easy to see how these powers have manifested in various mythologies as the gods. It's a great system too in that no pantheon is necessary, you can just invoke/evoke the planetary and zodiacal consciousness' directly. Not that the system is better than a pantheon based one, every representative of an original power, be it god or planet, has it's own distinct flair (if only because of the angle at which it is viewed).