I've mentioned many times before that I was -- and am -- a Traveller fan. It remains the gold standard for science fiction RPGs, particularly for those of us whose tastes tend toward "Imperial" style SF of the sort written in the 50s, 60s, and early 70s. I recently started to re-read the 1977 edition of Traveller and I was amazed by many things about it, but what most amazed me was the sense that I had never actually read these books before. Now, I know I had; I played Traveller a lot back in my youth and I owned copies of Books 1-3 in their original little black book format. Yet, re-reading made me think otherwise. How could this be?
Then it dawned on me. I didn't start playing Traveller till 1980 or 1981, well after the official Third Imperium setting had been firmly established. Alongside my little black books were later supplements, adventures, and copies of The Journal of the Travellers' Aid Society, each of which contributed bits and pieces of the Imperium setting, forever coloring my sense of what Traveller was and was about.
But there's none of that in the little black books. None. The Imperium is never mentioned. Like OD&D on which it was clearly modeled, Traveller in 1977 has only an implied setting, a goulash of Piper, Anderson, Tubb, Chandler, Niven, and Pournelle, with other bits and pieces ripped from off from SF stories written in the decades before the game was published. It's all very "pre-cinematic," which is to say, there's little to no evidence that science fiction movies or TV shows -- including Star Trek -- exercised much influence over Marc Miller in constructing the implied setting of the game.
So, yes, Traveller has a lot of socio-political-technological axioms in common with a lot of literary science fiction, but it nevertheless had no setting of its own. Indeed, the game frequently reminds its readers that it's the job of the referee to make one up for himself, using the tools included in its three rulebooks. (Ironically, this is a point on which the game is criticized in its review in White Dwarf #6). This absence of the Imperium, even merely as an example, makes a world of difference, believe it or not. The game feels far more wide open and flexible, two traits Traveller has always possessed in abundance but which become even more pronounced in the absence of the Imperium. This absence enables me to read Traveller with new eyes and that's a wonderful thing.