classic Traveller. Although I think I still have my original ruleset, I have no idea where it might be, so it was cool to stumble across this.
This book reprints the first three booklets from the original Traveller boxed set (the one with the "Free Trader Beowulf" quote on the lid): Characters and Combat, Starships, and Worlds and Adventures. It also includes the first five supplements--mercenaries, interstellar navies, scouts, merchants, and robots--and "Book 0," an introduction to Traveller and role-playing. This volume came out in 2000. It has a $28 cover price brand-new, but look how much I ended up paying for it:
OK, I don't know if it's actually his autograph, but I bought this book as a reader, not a collector, so the signed page was just a bonus.
These rules are what the kids call crunchy--with a lot of detailed mechanics on building characters, vehicles, ships, worlds, economic systems and even star systems. My favorite quote? This passage from Book 3:
The referee has the responsibility for mapping the universe before actual game play begins. The entire universe is not necessary immediately, however, as on a a small portion can be used at any one time.
I don't know if I'll ever get around to playing this, but there are plenty of ideas useful for other science fiction games. Stand by, Free Trader Beowulf--help is on the way!