Shadow of the Conqueror
I'm going to attempt to keep theis breif, becuase if I don't, I'll be here all day (and you'll eventually be bored enough figure out that the "Q" key makes the sword in the top left stab). Shadow of the Conqueror is my favorite book of all time ever sense I read it. The world is a singlt massive continent suspended in the sky, the sun does not move, there is no night, and the bottom and top of the world are connected. There are these two fictional materials, lightstone and darkstone, that behave strangely and are the core of the world's engineering. Darkstone becomes fixed in space unless light is shining on it, and lightstone emits light. Occasionally, the shade (evil creatures) harness enough power to make it night. People turn into shade without light, and our magical folk are useless without a bringer (a different type of majical person) or a lightstone to use as a battery because there is no more sun. Our main character is the defeated dictator of the world who repented and hid for the rest of his life turned into a young man and given lightbinding by some magical mistake while trying to finally end his life on his own terms at around 80. There is no way to take that story that is not interesting, yet somehow I am surprised by how things go.
The Stormlight Archive
The world that The Stormlight Archive takes place in is defined by it's destruction at the hand of highstorms, massive thunderstorms capable of tearing roofs off of buildings that get weaker the further they travel from the source (making plant and animal life extremely different across the continent). Highstorms make it dificult to travel on the open sea, to take a trade caravan not capible of attaching itself to the ground, and build structurally sound houses (among other things), but they are the only source of magical wizard juice (called stormlight). Additionally, there was an ancient race of honorable knights known as the Knights Radiant that suddenly left somehow and left behind some seriously OP gear, known as shardplate and shardswords. When you add 5 different flavors of lightbinding (2 of which each lightbinder gets) and some surprisingly good engineering, you get the most belivable fantasy setting I have ever encountered.
This probably dosen't deserve to be here because it's not high fantasy, but Star Wars was so good at making the universe seem huge that it spawned an entire extended universe full of more contant than anyone could ever want... Which Disney scrapped for a marginally worse one where they forget the timeline. I mean seriously, Mando's mentor would have fought jedi regularly, but she talks as if they were this ancient race. Anyways, Star Wars (4-6) masterfully makes a huge feeling universe without constantly making the new fan feel dumb. Then they spent 1-3 making the universe rather than good diolouge, but that's why 1-3 are my favorite, because they captured the imagination of a hyperactive child like none other.
The Book of Tashi
The Book of Tashi is something. I'm not really sure how to describe it. If I had to take a gander I'd call it feudal China with magic creatures, but then Tachi emigrates to something like vaguely "modern" America where he tells stories of things he's done to his new best friend. It's presented as a bunch of stories, and I never actually noticed how odd the premise was untill I just tried to explain it. Tashi tells of how he bounces around a world of adventure by being "brave, bold, and the best!" - The back of the Tashi book that happens to be sitting on my bookshelf next to me, as he tells of tricking demons, giants, whiches, and a war lord while befriending ghosts and anybody nice by acting far more trusting than he is. All in all, it falls in this strange area of "technically a children's book" but one with such charm and maturity that it can be enjoyed by anyone. I've never read fiction quite like it