The following is my comment to this post on Charlie Stross's blog.
I'm going to play devil's advocate here and try to argue against all your points -- not because they aren't justified, but because I've had far too much caffeine today. Hopefully the result will be coherent and not too ranty.
1) The power-chords of sci-fi are in many ways a bad thing. It doesn't make sense to classify everything with prominently featured space ships or robots as science fiction (as I think you said before in a rant about Star Trek). Action movies with robots are just action movies. While it has historically been useful to have these bits of shorthand, the fact that people could easily turn these things into hieroglyphs and expect a stylized silhouette of a rocket on the spine of a book to be almost universally understood as code for "shelve this in the science fiction section" is an indicator of just how little depth these things have.
So far as I can tell, the flooding of the market by crass commercializations with all the apparent symbols of the genre but none of the guts is not new. Maybe it's become a bit more common now that action movies in science fiction drag (and romance novels in fantasy-horror drag, and action movies in cyberpunk drag) have become so profitable, but looking through the science fiction section of a used book store yields an enormous quantity of slim volumes by (righteously) unknown authors whose prominent placement of space ships on the cover and use of terms like "groundcar" and "zeerust" instead of "car" and "rust" are the sole saving grace that put them into the science fiction section rather than the slush pile of a much more selective general-audience-fiction section.
Perhaps this is a foolish and egotistical position to take, but I've always associated science fiction with a kind of intellectual daring and experimentation. Naked Lunch had no space ships, but was classed as science fiction because it was too weird to be placed next to this week's new best-seller in the general section. While a lot of the groundbreaking science fiction of the golden age focused on space exploration (or at least had it as a major background element), both earlier and later science fiction did not. Is it justified to stick a starship on Neuromancer? What about on Odd John?
Using these power chords as shorthand for the entirety of the genre is occasionally useful, but I would argue that it's gotten to the point where it is far more misleading. Someone who has a strong interest in Halting State may have little to no interest in Hyperion; they are very different books with very different styles set in very different worlds, and it's questionable whether they should even be classified as the same genre.
This brings me to my next point.
2) The fragmentation of genres into overlapping tags is good for authors, for readers, for booksellers -- for everybody except the people who are shelving books by hand in brick-and-mortar stores.
While the science fiction section is a ghetto to be sure, it's a ghetto of ludicrous diversity. Someone who buys science fiction off a list of science fiction in order to stock the shelves of a science fiction section will get a handful of paranormal romance, a handful of action/adventure with a nominally science-fictional setting, a handful of cyberpunk, a couple books like those of Butcher's Dresden Files series (which are a cross between two genres, neither of them science fiction, but often get filed under science fiction anyway), and -- if they're lucky -- a couple books that get filed as science fiction purely for the weirdness factor (like Lethem's Amnesia Moon or anything by Pynchon or Ballard or WSB). Chances are, anyone who goes into the science fiction section because they like a particular kind of science fiction will find nothing of particular interest, unless they are very open-minded or very easily amused.
Part of this may be because the fragmentation of the genre, when first it gained legs, was extremely successful. Cyberpunk took off and showed science fiction that a book could be successful without a space ship shoehorned into it or a raygun-wielding pinup on the cover. The tendency for science fiction books to put in all the elements as though off a list -- this took a bit of a nosedive. (I am speculating a little here, since I cannot easily perform quantitative analysis of trends in the frequency of unnecessary instances of starships, rayguns, and robots versus properly justified instances of the same!) If fragmentation is encouraged even more, we'll still have the power chords: they just won't be used so often for the sake of classifying it into a particular genre.
PKD is perhaps an early example of the trend I see as a whole. Early PKD stories invariably had space travel and robots, regardless of whether or not their existence in the story was justified. But, a sequence of what is often considered his best work follows a very noticeable trend.
- The Three Stigmata of Palmer Eldrich had space travel quite prominently, and much of it was justified.
- Ubik had space travel prominently in the very beginning of the book, and had no space travel at all for the entire remainder of the book, because bringing it in would not be justifiable.
- The Man in the High Castle had space travel as a background element, but it was not prominent because it could not be justified.
- A Scanner Darkly, despite being set in the far-off year of 1992, had no space travel and no robots. It was clearly science fiction, but limited the science fiction elements to those that were necessary for storytelling -- very different from earlier novels, in which robot cab drivers were everywhere and cars flew and things took place on Mars for no clear reason (sometimes breaking fairly well-defined physical laws in the process).
But, if science fiction as a genre is not cohesive enough to merit being listed in the same section, how is a science fiction fan going to become exposed to authors they have never heard of?
3) There is a very good reason, from the consumer perspective, to go to a brick-and-mortar bookstore and look through their poorly-curated and half-assedly-assembled science fiction section. It is the same reason, paradoxically, that it is desirable that amazon's recommendation engine not be perfectly accurate.
I will again point out my assumption that science fiction is the domain of daring neophiles with strange ideas. Perhaps people disagree with me on this and would instead I call this by some other name -- after all, science fiction has a long history of referring to two completely different genres with occasional overlaps between them: the genre of daring neophilic explorations of strange ideas, and the genre of people with robots and space ships and laser guns. I'll call the latter 'raygun adventure' instead, for the sake of avoiding confusion.
Someone whose primary interest is mystery novels (or whose primary interest is raygun adventure novels) may not have any particular problem with reading many takes on what amounts to the same book. A police procedural can be fairly formulaic, and many popular police procedurals are: the interest comes from the emotional drama, from dramatic tension, from not knowing the exact details of the ending, or from knowing the exact details of the ending.
A book that plays primarily with the emotions of its readers can be extremely successful without giving the reader any new information, or even having any kind of consistent internal logic. Porn remains arousing even to people who realize that pizza delivery boys rarely manage to seduce lonely housewives, and The Kite Runner managed to be disgustingly disturbing despite the problems inherent in the idea that a former Nazi could be a small child in the 1970s and want to join the Taliban in the 1990s.
Science fiction is different. The one defining factor in science fiction is that it attempts to be information-rich. The characters and plot can (and often do) hang on the world-building or the conceit.
- Dune drags on endlessly, has numerous minor inconsistencies, bases itself around ideas like the existence of a secret sorority of NLP-masters who seed myths and plot to control the universe... but, it's just so damned interesting when the implications are explored that the predictable and recycled plot, the dull language, the all-pervasive humorlessness, and the occasional forays into incomprehensible non-sequitor are excused.
- Altered Carbon has many instances of weak writing, and a plot that's fairly tangled. It has enormous numbers of scenes of gratuitous sex and violence, and many of them seem entirely out of place. But, as a thought experiment it's incredible. The fact that it features what amounts to body transplants does not make it science fiction. Altered Carbon is science fiction because it points out that the existence of body transplant technology would fundamentally change the insurance industry, make it possible for the extremely wealthy to be essentially completely immortal, almost completely wipe out the Catholic church as a political and religious power, and still wouldn't solve problems like mood swings and menstruation.
The solution may well not be to make recommendation engines more accurate. While recommendation engines more useful the more accurate they are up to a point, to be sure, within the domain of science fiction recommendation engines are more useful the less accurate they are (up to a point).
Science fiction as a genre only ever worked because there were hardcore fans who would read books about space ships *and* read books about automobile accident fetishes. A regular genre reader would not be able to push his or her way through Rucker's Software were he only interested in robot books, or space ship books, because he'd get stuck on the parts about cannibalistic cults and recreational drug use and anarchism.
While other genres may be syncretic by accident, science fiction is defined by its syncretism. It's defined by its mashups. Anything that looks like science fiction, by definition, isn't.
If it has space ships and robots, it's probably an action movie. Don't trust anyone over 30.