You're right, Claybor, there isn't anything wrong with that. Unfortunately, this game's lore is spread out across multiple versions and varying book types. Some of it is in adventures, some is in sourcebooks, bits are in campaign sets. It's all over the place. That's kind of the thrill of it, actually. You have to dig up all this apocryphal stuff and you find out more and more as you read. You find an old copy of MegaTraveller Vilani and Vargr and learn things about the Vargr Extents and the Vilani humans. You nab a beautiful, near-mint copy of Classic Traveller's Alien Module 4: Zhodani, and find out about their cool history. You luck into MegaTraveller Journal 3 and learn about the awesome tech level-16 world of Vincennes. The list goes on. After digging around, you learn all this cool history, see new ships, gear, planets, aliens, etc., some of it a little goofy but most of it pretty darned great, and it all adds into your game.
Is it summarized in one tome and easy to obtain? No, obviously not. But you really don't need it all. Find out about one sector where you want your Travellers to adventure and get into it; while doing so, find more of the old stuff and read through it. I'm telling you, it's like finding rare treasure. And then in your next adventure, add some of that in. Traveller is like a fine dish that you cook up that keeps getting better and better as you find more rare spices to mix into the broth. I'm sorry that that probably isn't very satisfying to you or your players, but if you stick with it, this game has payoffs that surpass those of most other RPGs.