First - the Classic Traveller Bundle of Holding is back, this time with supplements instead of adventures. CT had some pretty interesting features; if you already have Mongoose, it might be worth checking out for historical perspective and potential houserules. I may have to dig through the supplements on the upgraded tier.
Second, I stumbled across this very, very interesting article from an old scifi webzine discussing the inspiring works for Traveller. The author concludes that Traveller has always been hard science fiction noir, with a focus on the criminal and the political dissident, and that its two primary literary inspirations were the Dumarest Saga (which I'd never heard of before, but is evidently the source of low berth and the whole non-ship part of the game) and H. Beam Piper's Space Viking, which I've heard of but not read. I think the article makes a pretty convincing case, and also explains where a lot of the odd Travellerisms like mesh, blade, and feudal technocracy come from. Definitely worth a read, and not just because it supports my conclusions that Traveller is intended to be about cash-strapped antiheroes doing jobs of dubious morality to make the next payment. I suspect a clear understanding of where it comes from and why it made the design decisions that it did might be important for successfully upgrading Traveller.