Well, the current (first) edition of Mongoose Traveller is a full game with only the core rule book.
Also, you can still get "The Traveller Book" printed from RPGNow!, which is pretty much the same as the Mongoose version in terms of scope, but using the "classic" edition of the rules from back in the 80's. This is an "Old School" RPG though - characters die a lot, and there is no guarantee that player's characters will be at all "balanced" against each other. And yes, this is the edition in which you can actually die during character generation, and there are algebra equations and vector math diagrams in the space travel section.
Mongoose's edition has a more entertaining character generation sequence and is easier to digest, though as usual people have quibbles with some of the rules. (Which is pretty typical for Traveller - it seems nobody plays any edition "stock".) Mongoose Traveller is the closest thing to "Classic Traveller" that I've seen while not actually BEING "Classic Traveller", and many people find that it fits the modern RPG gamer's mindset better than cruchy ol' lethal Classic.
The 2nd Edition of Mongoose Traveller that's just now appearing can be played with only the core rule book, and I like the direction they've evolved the rules for the most part, but a fair amount of the basics (most notably starship creation) is slated for later books.
To be fair, people disliked the fact that "Classic" and "1st Edition" had two different spaceship design sequences, so dropping the "quick and dirty" system wasn't a completely illogical choice.