From Introduction:
All role-playing game systems present a "default setting," that is, the "world" of the game. Some games even present more than one such setting. Most classic and modern fantasy RPGs are developed from a common Eurocentric fantasy setting that mashes together the works of J.R.R. Tolkein, Jack Vance, Michael Moorcock, and to a lesser degree other classic authors of fantasy fiction. Most science fiction role-playing games, on the other hand, are set in some recognized literary, television, or cinematic universe; the sad thing about this is that, in such a universe, the heroes are already known quantities. No matter how dashing or capable an adventurer in one of these games might be, he or she will never be the true hero of the story, and this fact can be very disappointing.
But what can be done about this? Unlike fantasy worlds, where we have common traditions and myths to give them flavor, a science fictional universe generally depends on some work of fiction for its flavor. There is no common science fictional universe, it would seem.
This is not so. Before the rebirth of science fiction on TV and in the movies, which started in the late 1960's and really didn't get rolling for another decade, there was one commonly-understood science fictional universe: epic space opera, set in a human-dominated galaxy. Curiously, while authors such as Isaac Asimov and E.E. "Doc" Smith are famous at least in part for their galactic civilizations, Jack Vance was one of the most prolific writers of works set in a human-dominated Milky Way galaxy. His works in particular present a galaxy too large to be governed by any one central authority, with far too many inhabited planets to comprehend, and unlike many later fictional works, his books often featured people and stories spanning mere handfuls of worlds. In such a galaxy you can find almost any adventure, and there is room enough for an endless variety of heroes and villains.
So that is the default, implied setting of this book: a human-dominated galaxy. Player characters presented in this book will be human, more or less, living human lives on worlds sometimes green and pleasant, sometimes weird or inhospitable.
Some Game Masters may wish to incorporate aliens, mutant or genetically engineered humans, or perhaps even robots or androids as player characters. This book explicitly omits them, for the sake of simplicity; we plan to include such characters in supplementary works. Whether or not any Game Master chooses to allow such characters depends entirely on what kind of galactic civilization he or she wishes to present. Are humans the only species with FTL travel? Indeed, are they the only sentient species in the galaxy? Or perhaps humans are just one of many species exploring space, fighting or trading for habitable worlds and other resources.
The galaxy is huge, and the possibilities are endless. Strap on your blaster and climb aboard your starship, for adventure awaits among the stars!