I've been reading the Mongoose version of the Traveller rulebook lately, and I feel that it's pretty close to the original. For an old school game it doesn't lend it self to easy free form play though. I think I remember that the original was like this also.
When I first bought traveller, I bought the starter edition. This version didn't have any reference to the Third Imperium, it was just a generic sci-fi game. To this day, I'm still unfamiliar with the Third Imperium setting, but I have no problem with getting into it.
While searching the web for further Traveller knowledge, I came across this. BITS (British Isles Traveller Support) looks really interesting. I like that they are producing new material for the game, unfortunately it doesn't seem like any of their stuff is available in the U.S. I like that they call their books "Little White Books", as a contrast to the little black books.
If you get the chance, check them out. I plan on contacting them to see if any of their books are available in the U.S.