Legends & Lore is an old-school D&D book that takes real world pantheons of gods and adapts them to Dungeons and Dragons. Which raises one obvious question - exactly how much cultural appropriation are we talking about here?
The answer: not as much as you might think. Ultimately, there's not enough culture in this book for it to appropriate much of anything. Each of the gods gets perhaps a paragraph or two to explain who they are and what they do, and then the rest of the entry details what it would be like to fight that deity.
It's an odd choice. The introduction to the book claims that it's not meant to be a Monster Manual, but rather a resource for DMs interested in worldbuilding, and that claim half checks out, because the actual divine stats are so ridiculous and over-the-top that no reasonable adventuring party would even come close to beating them. And yet . . .
This book is structured exactly like a Monster Manual. The individual entries for the various gods are Monster Manual entries. There is almost nothing about their relationships, theology, or role in the functioning of a campaign world. They might not be there for players to fight, but that is pretty much all the information in the book is good for.
I think this is a book that had a lot more utility prior to the internet. None of the gods in the book, not even the really obscure ones, have an entry longer than their individual wikipedia pages. Which means that from a modern perspective, a quick google search is about 100 times better than anything this book can do for you. But perhaps things were different in 1983. Perhaps, back then, a book like Legends and Lore would have been useful as a mythology index, even if it's not a great primary resource. I can imagine that if you were a kid back then, faced with the daunting prospect of a gigantic card catalogue to search through, then maybe it would help to see a drawing or a name or a brief power description in this book and thereby become inspired, allowing you to narrow down the questions you'd ask the librarian while doing your research.
In any event, this book is now a relic. Useful to me mainly as a curiosity, a way to make my 1st edition AD&D collection look less perfunctory. The cover is awesome, as all the covers from this period in the game happened to be. The interior art is . . . inconsistent, again, as was standard from works of this period. The actual text, however, was far too lacking for me to ever consider it an essential resource.
UKSS Contribution: This is a tough one, because technically I have the bulk of human mythology. But if I confine myself to the details that actually made it to the page, my options are a bit more limited. I think I'm going to go with the cloud chariots of the Sumerian pantheon. They're not just a stylish form of transportation. According to Legends & Lore, they are also a way that the Sumerian gods identify themselves to their followers - if someone shows up and they don't have a cloud chariot, then they're not (verifiable) a god.
I like that. It shows real consideration on the part of the gods to include some form of error-checking into their divine appearances. I probably won't give the cloud chariots of Ukss to actual gods, per se, but I can see them being the proprietary magic of some mystic order, which uses this signature form of transport to verify their involvement in particular situations.