It's been 20 years since Bruce Sterling compared the "mainstream" of science fiction to a fossilizing Politburo. Since that time, the situation has only gotten more dire. People are constantly remarking on the graying of science fiction readership, but statistics seem to be hard to come by. Here's Tor's Patrick Nielsen Hayden talking about the fact that almost no people born in the 1970s or later have won Hugos or Nebulas. (And in the comments on that post, there's lots of assertion that WorldCon's attendees were skewed towards an older demographic, but no hard numbers that I can see.) Here's an amusing essay from the New York Review of Science Fiction analyzing an issue of Asimov's where every single story is by an older writer and is about getting old.

Meanwhile, young-adult science fiction is exploding. According to John Scalzi, the top 50 young adult science fiction/fantasy bestsellers sold twice as many books as the top 100 adult science fiction/fantasy bestsellers. As we mentioned before, there have been hardcore post-apocalyptic novels for kids and young adults for decades. With more on the way. And with City Of Ember finally being adapted to a (hopefully) major movie, more YA readers than ever will be looking for similar stories.

It's great news that young people are getting exposed to SF at an impressionable age, without apparently feeling any particular stigma about it. And yes, a lot of those people will eventually come to view SF as "kid stuff" and stop reading when they reach adulthood. But if even 20 percent of those readers keep reading SF after they turn 18, that guarantees a sizeable readership for SF in decades to come.

The other great thing about YA science fiction is that people come to writing it from all sorts of angles. Some YA authors write non-speculative YA books and then drift into writing books with science-fictional plots. Some "real" SF writers, like Cory Doctorow (and Scalzi, whose new book Zoe's Tale is being marketed to both adults and teens), try their hands at YA fiction. And then there are "literary" writers, who would never dream of trying to write a grown-up SF book, who find themselves writing for the YA market. I was having lunch with a literary author, an MFA who teaches creative writing and writes for journals like Ploughshares, and she was telling me her agent had told her the big New York publishers were looking for YA books with scifi or fantasy elements, and she was trying her hand at one. Dale Peck, who's now co-writing a science fiction novel with Heroes creator Tim Kring, started in speculative fiction by writing the scifi/fantasy blend Drift House series, about time-travel and a tapestry that shows the future.

Meanwhile, "science fiction" as a publishing niche refers to a segment of books that appeal to a particular segment of people. Call it "nerd lit." You don't have to be a geek to read science fiction - just like you can dress in Banana Republic and listen to Death Metal or Goth/Industrial music. It just helps. You're more likely to find your fellow Vernor Vinge enthusiasts at a gathering of sysadmins than at a dressage meet, or a stockbrokers' convention. Science fiction is stories written by geeks for geeks. (I'm a nerd myself, so I'm not being obnoxious here.) Your average SF novel nowadays assumes you belong to that culture from the outset, and you're used to a whole range of concepts and stylistic tics that might put off other readers.

Luckily, we can have both grown-up science fiction and the YA version. But to the extent that one is shrinking and the other one is growing, that may not be entirely a bad thing. Look at it this way: is it better to have SF written for a subculture, or anybody of a certain age?

The readership of "regular" science fiction books is a defined group of people with a shared set of interests, who dress a particular way and talk in a "nerd accent." The readership of YA books is anyone of a particular age. So, in a sense, YA books have a more diverse readership and are more welcoming to outsiders. Grown-ups might feel silly reading a Scott Westerfeld book on the subway, but there's really nothing to stop you doing it anyway.

Bottom line: We're lucky to have both YA literature with science-fictional themes and "regular" science fiction. There's no reason we can't have both, and appreciate both for what they are, including the innovation and breadth of concepts that mature science fiction can explore. But we should especially celebrate the awesome potential of YA SF to revitalize the field, and bring new readers to SF concepts.

On its surface, The Dark Knight is a typical franchise sequel, bringing in (familiar) new characters and amping up the Bat-action as we move from the race car fu of Batman Begins to this flick's awesome truck-and-motorcycle fu. Our central figures, the Joker and Gotham's "white knight" district attorney Harvey Dent, are perfect foils. The former is unfathomably evil and the latter unfathomably good. And for a while the balance between these two, with Batman hovering in a profoundly unstable place between, works to good (disturbing) effect. Dent is the unmasked hero that Batman could never be, leading us to question Batman's dubious vigilante tactics in the first place. And Joker is the supervillain Batman could never defeat because his love of mayhem draws out the worst in our dark hero, turning him into a sadist.

In these early moments, we watch mesmerized as the Joker — played with a kind of understated grunge Nihilism by Heath Ledger — unfurls his super-serial killer consciousness in acts so horrific they cannot be motivated by anything as logical as money or power. When he cackles to Batman that he is an "agent of chaos," the cliched phrase follows on such creative acts of destruction that it comes to you in the form of an original idea. Yes, you'll find yourself thinking, there could actually be an agent of anti-order, a force that exists only to topple structure, something that is neither good nor evil but just pure psychotic energy.

And Harvey Dent (Aaron Eckhart) really is Joker's opposing force, not Batman. Dent is the DA so crazy with reformist urges that he's willing to take down hundreds of mob honchos all at once. He's positively nuts with hope, maniacal in quest to wipe out crime without considering the consequences. Because when you take down the biggest mob bosses and suck all the money out of their secret Hong Kong investments, they turn to the guy with the freakiest plan. They ask the Joker to make Gotham City safe for organized crime again. And that's when things get really, really ugly.

At its best, Dark Knight is really about the tension between Joker and Dent. Batman is a spectator, forced to consider the possibility that he's no longer needed in a town where Dent rules — and that he cannot ever win against the evil created in a town where Joker does. Bruce Wayne, Batman's secret identity, does a lot of soul-searching about this. And his uncertainty is part of what makes this film so incredibly dark. What do we make of a hero who has outlived his usefulness, whose torture tactics when Joker is in prison turn out to be disturbing replicas of what we condemn when we read about it happening in Iraqi prisons?

Of course it turns out that the Joker/Dent binary has to collapse, and finally Batman must return in an even more horrifying, morally-compromised form. After the Joker and his mob buddies murder Rachel, who happens to be both Wayne's one true love and Dent's fiancee, Dent's maniacal hope becomes mere mania. His face half-destroyed by the Joker's attack, and his mind entirely addled by pain and loss, he becomes the supervillain Two Face who wants nothing more than to kill everyone remotely connected with Rachel's death.

And this is where Batman's motivations become far too dark to be those of a hero. He has to stop Two Face not so much to save the city (though that is a consideration), but instead to cover up the fact that the city's best hope Dent has become a murdering crazoid. His final mission in the film is a cover-up. And it's not surprising that he cobbles together the worst representations of the surveillance state to hide the truth from Gotham. He rigs up a system that allows him to turn every single cell phone in Gotham into a sonic surveillance device that feeds him real-time information about what's happening everywhere in the city. As preposterous as it is, the device is "real" enough that we recognize why Batman's mad scientist pal Lucius Fox (Morgan Freeman) says he'll quit if Batman uses it. "What about privacy?" he demands.

We get it: Batman has to go as dark as his enemies if he's going to stop them. Except Two Face isn't really his enemy. He's not even really a supervillain yet. He's got no henchmen, no plan, no secret weapon. He's just Bruce Wayne's favorite politician, a friend who has gone crazy.

This fact will continue to tickle at the back of your mind during the amazing fight scenes, filled with cool twists and awesome explosions, and a lot of truck-ramming. You'll revel in the cool ways Joker finds to escape from prison, blow up a hospital, and somehow manage to still seem humanly creepy rather than campily arch the way Jack Nicholson's Joker was so many years ago.

But you won't be able to forget that Batman is doing all of it to hide the truth about Dent. He's not saving the world, or even Gotham. He's just making it seem as if good guys never go bad; he's "rewarding people's faith," as Police Commissioner Gordon puts it. And in the end, he sheds his hero's mantle to take on that of the "dark knight," as if that is somehow an even more powerful position than hero.

It isn't, though. What makes this movie brilliant is that we know the Joker has won. Batman has abandoned all pretense of seeking justice, and instead seeks merely to create the illusion of justice. As he rides off into the night on his motorcycle of doom, watching the city through our cell phones and making sure we never know when something has gone wrong, we don't feel comforted or protected. We feel exposed to the rawness of another truth, the kind of truth you can really only find in a story that is pure, unadulterated fantasy.

Good guys lose. The only way to survive is to accept the darkness.