I've been thinking lately about space opera.
Specifically, I'm wondering if there's a formula to it, the way there is for epic fantasy. Both are forms or genres that seem to prefer large, sweeping stories spread out over multiple books. Epic fantasy is perhaps more known for multi-book storylines, but I can equally point to epic space opera stories, like Dan Simmons's Hyperion Cantos or Peter F Hamilton's Night's Dawn trilogy. There's also the notable case of Stephen R Donaldson, who's known for both the Thomas Covenant books (epic fantasy) and the Gap novels (space opera).
Admittedly, I've read very few of those books above - I loved the Hyperion books, but was less taken with Night's Dawn, and have never gotten around to the Gap books, though I keep meaning to. My experience of space opera revolves more around other media, specifically TV (Star Trek), movies (Star Wars) and video games (Mass Effect), which tend to skew more toward the mystical elements that epic fantasy also shares. Heck, Star Wars even has magic in it, and features a farm-boy toppling an empire.
But there are enough similarities to begin to move toward a unified definition of space opera, and chiefest of these seems to be multiculturalism (or at least politics, since alien races aren't present in much of Hyperion or Battlestar Galactica). Even the Ender/Shadow/whatever else novels by Orson Scott Card mix characters of different (Earth) cultures and find narrative momentum by examining how they interact.
Another common theme is hyper-specialized Earth analogues. Hyperion's setting is full of planets that are based on one specific aspect of Earth culture, and so is Night's Dawn - in fact, that's one of the things that put me off about it in the first place, as one of the planets in question has recreated Victorian-era British culture, an idea I found stretched credulity far more than the idea of the dead rising and invading human space. Go figure.
Star Trek leans less in this direction, though there are some notable episodes that glance at this kind of idea (like that early episode of TNG with the African-derived culture). Likewise, Star Wars doesn't have much in the way of Earth-cultures, but its equivalent is the array of landscapes it uses to show alien planets, from Tatooine to Dagobah to Endor.
The intersection of politics and business is another big theme, though not in Star Trek, where business doesn't really exist (a fascinating idea on its own, and one that seems to have been explored only there and in Iain Banks's Culture novels). Or if not politics and business, then the politics behind certain galactic corporations' misbehavior seems to be another favorite theme. It feels like a more recent addition to space opera, but timely, as the role of corporations in our own politics grows ever-larger.
Fantasy, meanwhile, seems to have started to embrace talking about business only in the last few years, the main example being the books of Daniel Abraham (whose favorite theme seems to be economics in general). It's probably less relevant to that genre as a whole, but does provide some thematic tension in the form of modernity versus tradition, similar to how it must have played out in actual history.
Daniel Abraham, in fact, is one reason why I'm setting my thoughts down like this. He famously held a discussion on how epic fantasy works with a number of other New Mexico-based SFF authors a few years ago, and the result is his series, the Dagger and the Coin, the last book of which I'm currently reading now. I'm fascinated by looking at the themes in common of space opera, not just because I like it but because it's a form I'd like to try my hand at, and I think an understanding of the tropes and themes is a good starting point.
So let me throw the question out to anybody reading: what space opera stories should I read? And what themes or ideas have I missed?