I've been re-reading the two Tekumel novels by M.A.R. Barker - Man of Gold and Flamesong.
As books go, they're pretty enjoyable. Not the best fiction in the world, but the stories are interesting and the world is extremely well detailed.
Ultimately, that's why I like the world but I'm unlikely to run anything in it.
Why I like it. The world drips with interesting and well-connected detail. It's clearly well thought out, and nothing reads like a retcon or half-baked idea. How could it? So much of the world has been thoroughly thought out. It makes it an interesting place to read about, and probably to play in as well.
Why I probably won't run it. The world drips with interesting and well-connected detail. Their is clearly a pretty big canon that, as a GM, I'd feel compelled to achieve a good command of. I could just make stuff up, sure, or pass it off as mis-information later ("Sorry, that guy was just wrong.") But I'd still need a lot of digging and reading and checking to get it "right." And if I didn't get it "right" I'd feel like I was not doing justice to either the setting or my game. It's fine for the players to be foreign mercs utterly unaware of the setting and learn as they go . . . but I can't GM that way. And once I start making stuff up, and letting my players make stuff up, the well-connected detail of the world becomes more and more of an obstacle to me. I'd rather make stuff up in play without reference to someone else's world.
So, yeah, as much as the books are a good read and the world looks like an awesome place to explore . . . I'm just not convinced it's worth the effort of learning someone else's world just to have my own game. I understand others disagree - strongly! - but for me, it's a lot of work and I don't think I'd feel happy with the results of the work. That said, I'm still going to steal cool stuff from the world - my players dealt with stinky Ahoggya in my last game . . . and may again!