Tékumel was basically the first (and may I say: one of the coolest, definitely cooler than The Forgotten Realms, though that's because Wizards messed it up to fit all the D&D fans' tastes, it was no fault of Ed Greenwood), world to be published as a roleplaying game. Since the Blackmoor and Greyhawk supplements didn't really include any information about those worlds, rather than extra rules and monsters that you can use if you want.
Tékumel was created by M.A.R. Barker, who was a professor like Tolkien, except Barker was a professor in more Meso-American cultures and Asian cultures, and basically created a reverse Tolkien world: one inspired by Meso-american and Asian cultures rather than western ones and Nordic and Saxon ones. This was before Maztica, and it's very upsetting how M.A.R. Barker doesn't get mentioned as much as he should be: for goodness sakes, he created whole languages for his world, whole histories and artworks. Tékumel equals Middle Earth and Arda in greatness and depth (he created thirty ways of saying "you" in one of his languages). Additionally, he created a new, weird, and interesting sub-genre of fantasy, at least in the gaming world. And, anyway, Tékumel was still weird compared to other settings like Tékumel that use the same type of inspiration.
I hope you'll come across Tékumel sometime and buy and try it out. He also wrote three novels, however he was much more about the world so they were never huge successes (i never read any of them, though I want to). But, the world makes up for everything. Be aware that Tékumel often goes under the name: Empire of the Petal Throne.
Happy gaming and love Tékumel!
Darnanc: Nilchal wila.
Definition: An adult girl.