While not disagreeing with the other answers, it is worth pointing out that other than the archaic White Box D&D rules framework, the original rules are about the most playable version of the game, and costs about $25 in reprinted form.
The Swords and Glory books are almost twice the cost (each!) and unless they have been retypeset they are pretty hard on the old eyeballs. I think the originals (which I own) were mimeographed from typewritten originals, and neither of them has an index. They come from an age when codifying every single thing was thought to be a good way to go for RPGs - think AD&D meets GURPS on steroids. My opinion of them is that they make reading your local tax code look interesting. The information is in there, but finding it is a journey you may assess as time you'll never get back. S&G was envisioned as a three volume set. Only two of the three ever saw print.
The Guardians of Order book is very nice, but very incomplete when it comes to the Bestiary. It doesn't even cover all of the intelligent races introduced in the TSR first edition. It does have a nice world map in the back cover. I found the Tristat-derived game system to be unfriendly. It took me over an hour to generate my first character. The system offers a complexity in its combat system I do not find attractive. Your mileage may vary.
Were I going into the Tekumel game again (and don't think I haven't tried to interest people in playing therein) I would be tempted to use the original EPT (available at http://www.tekumel.com/tita/ept.html ) and do a quick port into Savage Worlds. Total load: about 40 bux and a little work.