Since Adam asked me to, here are some thoughts about Tekumel, specifically regarding dealing with setting intimidation.
For those who may not know what this is about, Tekumel is a fantasy/science fiction setting developed by M. A. R. Barker, a now retired Professor of Linguistics. He started writing and playing childhood games in it sometime in the 30s, as a little kid, and continued work on it for pretty much his whole life. At some point in the 70s, he got involved with the emerging RPG scene in Minneapolis, with Gygax and Arneson, et al, and it became a game setting.
The setting itself is quite unique, but has influence ranging from classic pulp SF, to Aztec and Mayan cultures, to Moghul India, and a lot more besides.
Given it's age and near constant development (Barker wrote at least 5 novels, and ran a weekly game for decades), there is a huge amount of setting material available. This has led (along with some unfortunate developments in the fan community) to the impression that it is unrunable by anyone other than it's creator, or at the very least, that it requires huge amounts of research and learning to run "right".
This is not in fact the case, although I can see how one might get that impression.
The amount of material should be seen primarily as a resource. It kind of makes me laugh when I hear folks who in other contexts complain about the dearth of material for other settings turn around and complain that there is too much for this one. I get that it can be intimidating. But really, it's just like any other game setting; if it inspires you, take what you like, ignore the rest, and have fun.
That being said, I've been trying to come up with a pocket description of what I consider to be the most important bits, to help newer players and GMs have a framework to guide them. Here are some notes on this.
First off, this is an alien world, terraformed tens of thousands of years ago by very powerful spacefaring humans. The native plants, animals, and sentients (all very hostile and toxic to humans) were greatly harmed by this, but managed to adapt and survive here and there. The humans had many alien races working with them, and some against them, that also ended up on this world. This piece is perhaps best understood through the lens of classic pulp SF; think Ming the Merciless and you'll get the general feel.
At some point, a great cataclysm happened, and the whole kit and kaboodle was thrown into a pocket dimension, causing a great dark age. The stars went out. Technology failed. Great paroxysm shook the world, and for a very long time, human (and other) life hung by a thread. Slowly, civilization emerged again, but what technology remained was now more or less magical to the survivors, and the overall technical level was medieval at best. So, this is also a setting that could be considered post-apocalyptic.
During this time, two things happened that really changed things. First, people figured out that they could access other-planar power, i.e. magic. And second, contact was made with vastly powerful other-planar entities, i.e. Gods. These beings are hugely more powerful than anything else, but seem to take an interest in this world too. This, I think, constituted an existential crisis for the humans here - in a world where the Gods are real, and take action the world, but also don't care in the least about individual humans, you have a sort of nihilistic situation. More on that below.
The current setting takes place 60000 years after the cataclysm. Empires have risen and fallen during that time, many times over. The current cultures of this place are still, to a great extent, trapped in the nexus of the events described above.
To sum things so far...dangerous planet. Insanely high tech level now considered magical. Apocalypse. Real magic, and real gods. Huge amounts of time having passed and things still not looking very good for the humans.
Culturally speaking, the current batch of empires (there are 5) can be seen as reactions to all the above. Survival of the species in a world where humans don't really matter on any existential scale is still a paramount concern; but we see this primarily in the social structures of the societies, rather than in any explicit way.
Because, you see, the vast majority of humans now have no idea any of this stuff happened. All they know is that things are the way they are, and have always been that way.
And how are things? Well, first off, the main unit of cultural organization is the clan, not the individual. This is a society where individuals don't matter as much as the group. People define themselves by the groups they belong to. Your group is how you survive.
Status and relative rank are super important. These people know their place, and know that staying in the bounds set for that is how you survive.
The lack of any "good god" or moral absolutes means that they have a rather different understanding of right and wrong; noble action is doing what you say you're going to do, within the bounds of class, status, religion, and group affiliation, and ignoble action is not staying in those bounds, like you're supposed to. This means that if your god demands human sacrifice, that's noble for you to do. To refuse would be ignoble, as would performing human sacrifice if your god doesn't demand it.
The good news, such as it is, is that these societies are really very diverse, and quite accepting, so long as there is a slot defined for whatever behavior is in question. The important thing is that it's classified, controlled, and understood.
Likewise, for nearly everything, there are rules, and also exceptions. For example, violence between the temples is not allowed. Except for underground, in the wilderness, and really, when no one is watching. Then it's understood that it's ok. Similarly, women are generally meant to stay at the clan house, raise kids, and not participate equally in society, except that they can, at any time, declare themselves "aridani" which make them legally equivalent to a man, and then they really are.
All of these things can be seen as a way for society to provide some sort of stability and predictability in an otherwise unrelentingly hostile world.
There are if course lots of details. There are no riding animals. Slavery is common (as much as 20% of the population). Literacy is very low (10-15%). Metal is rare, so they use the hide of a big triceratops like creature to make things like swords and armor. People here aren't Caucasian, and are generally tan-skinned, with straight black hair and dark eyes.
All that stuff can be understood reasonably easily, and a good introduction to the basics of what's different on that level can be gotten from any of the basic rule sets that have been published over the years, or via online resources.
What I hope to have accomplished here, though, is to provide a framework for understanding what you might read about this setting, and convince you that while it's quite different, it's not impossible to use.
In fact, it's a hugely rich setting for games. Most recently, I've been exploring the history of a young aridani woman, from a rural town, as she grows up, travels to the big city, becomes embroiled in her clan's politics, falls in love with an older man, and struggles to find a place for herself.
It is great for plain old adventuring, explorations of the underworlds of the great cities, fighting horrible alien beasts, dealing with ancient magics.
It is wonderful for intrigue - conflicts between temples and organizations, jockeying for position.
It's fantastic for military adventure, as the empires have rich military traditions, and skirmish with each other often.
I've even run it as a CoC style game of horror.
And, of course, I'm happy to chat about it. Mainly though, the above should be taken as an invitation to explore this setting...and to take what you want from it, make it your own, and go have fun.