A short write-up, Why build new worlds, which surveys the origins and of secondary creations such as Middle Earth.
One aspect of these attempts at world-building is the most detailed ones invariably borrow and reconfigure aspects of our own universe. This is obvious in The Song of Ice and Fire, and explicit in The Lord of the Rings, in which Tolkien was striving to create a mythology for the Anglo-Saxon peoples. Guy Gavriel Kay takes this tendency of drawing from our world to an extreme in works such as Sailing to Sarantium, which has numerous characters who are clearly modeled upon figures from our world’s history. Similarly, Kate Elliott’s Crown of Stars series is pretty obviously set in 10th century Germany. And she says so in the afterword of the first book if I recall correctly.
But one aspect of this borrowing from our own world is that like Tolkien there is a focus on Northern European source material. Since most of the buying public are probably white for English speaking fantasy that’s a reasonable choice. But sometimes you get an author who mines a whole different part of the world, and the result can be very fascinating. Martha Wells’ Wheels of the Infinite has issues with plotting and character development, but it’s imagining of a fantastical Angkor-like civilization is beautifully rendered.
If there is one area which I thought would be excellent source material for a secondary world, it’s the highlands of Ethiopia. I’d love to read fantasy which draws upon this land’s history, in a part because most people (including me) would not have as clear of a sense of who was based on someone real and the correspondence of events to those in our world’s history.
Speaking of fantasy that doesn’t borrow from European history, Ken Liu’s The Grace of Kings is quite clearly based (to a Guy Gavriel Kay-like extent) on the transition between Qin and Han and the life of Liu Bang. Being, at the time, unfamiliar with the ancient history of China I appreciated the book a lot, tho I’m not sure how it would feel now. I haven’t read its sequel yet, so I guess I’ll know in the future.
Paul Kearney’s Macht series instead is based on Xenophon’s Anabasis and then on the conquests of Alexander the Great, and I liked it well enough even though I’m very familiar with the original material (we translated Xenophon and Plutarch from Ancient Greek in high school, thank you Italian school system), so I suppose that no matter how much you know or can guess what’s going to happen, the author can still make a difference.
Robert Howard (who I think was one of, if not the first, to do fantasy as psuedo-historical fiction) supposedly started writing his Kull and Conan stories as actual historical fiction, but realized he didn’t have the time/resources to do the necessary research, and so stuck them in a psuedo-historical fantasy world where he wouldn’t have to worry about looking up facts.
The world of his stories is a lot more broad than the narrow medieval European focus of a lot of post-Tolkien fantasy, with stories taking place in African, Central Asian, Egyptian, etc. locals, and the world as a whole being inspired by the Hellenistic Mediterranean. Though its definitely all those places as seen through the lens of early 20th century European pop-history.