The appearance of Firefly in 2002 was a breath of fresh air; ignoring the tradition of latex-layered aliens and sterile societies in a formless future, Firefly offers a grittier view of a human frontier that had to reach back into the simpler technologies of the Earth to deal with colonization.
In the future, there are more neat toys, but humanity is essentially the same. (Which, to me, is an encouraging thought.)
Sure, I like aliens, but you don't have to look far in todays television SF market to see that aliens can be both a crutch and a huge liability to a show. Bumpy rubber aliens who act like humans, dwelling in a vastly overpopulated galaxy land such a blow to believability and mystique that it was a relief to see a show that was going to have to get around without them. (It also reminded me of some of the great SF literature that's out there sans aliens...if print can do it, why not TV?)
Firefly inevitably relied on the notion of a created/extrapolated world that *has* to hang together. By ditching not only aliens but much of the stuff that Buffy, Farscape, Trek, or a number of other genre shows have leaned on (time travel, telepathy, alien dimensions, et cetera) I felt that Joss was promising a story where he wouldn't cheat -- where a certain degree of realism was guaranteed, where a deus ex machina couldn't be trotted out for a cheap thrill, and where the drama had to come from the story.
Composition of the 'Verse
From graphics in the movie, 'Serenity', as well as from the books, 'Serenity: The Official Visual Companion' and 'The Serenity Role Playing Game' we are presented with a map of the 'Verse which is a star system composed of several stars, of which at least five have orbiting planets. This is supported by Joss Whedon's shooting script presented in 'Serenity: The Official Visual Companion' (page 113) which describes the map in a scene from one of River's flashbacks, as follows: "Slowly she looks down at her desk. On it is the solar system, glowing lines connecting all the stars and planets."
Room to Grow
Yes, some of the setting details have been left vague:
The Unification War
There are two episodes in the Firefly series that show the Unification War. The intended series pilot, "Serenity", begins with a battle between the two factions at a place known as Serenity Valley. (It is from this battle that Mal's ship gets its name.) The Browncoats represent the Independence movement and the Alliance represent the core worlds fighting to unite humanity under a single government authority. Mal and Zoe are fighting for the Independence movement and through a colossal series of apparent bad luck, so many Browncoat officers are killed that Mal, a seargent, assumes command of the regiment. Although they put up a valiant fight, the Browncoats are ultimately defeated and the two sides negotiate peace — while leaving their armies in the field (think casualties).
The second episode that shows part of the Unification War is "The Message" where short scenes are shown of a battle with Mal, Zoe, a fellow enlisted soldier named Tracey, and a commanding officer who appears to have cracked under the strain of battle (he mutters about his arms being missing, even though they're still attached). The Alliance seems to have the upper hand...and a lot of cool toys that you need to run away from quickly.
Speculation: Strangely, most of the glimpses of the war we've seen so far (July '05) suggest that Browncoat officers have a short survival rate in battle. Combined with the strange clues from River, it might be possible that the Alliance's experiments on her may be part of a larger and more dastardly long-range program to control events. (Note: Larger because River was not old enough to have been part of the war, so if true, there must be more psychic soldiers somewhere.)
From the first episodes I saw Firefly as a rich world for roleplaying. 99% of any SF aliens are transparent analogs of familiar peoples (and usually racist versions of those familiar cultures). In the 'verse, humans are the good guys and humans are the bad guys; thatís easy to understand and follow. For the gaming aspects, there is enough conflict to fuel hundreds of stories. There are dozens of choices for lifestyles and options for character development. In working on a Firefly game, I tried to work out a simple gaming engine that focused on basic mechanics for knowledge, actions, and tools (including weapons). I enjoy games and settings that focus on individual initiative and freedom rather than a massive rules set, and Firefly is definitely that kind of setting.