According to the local Borders or Barnes and Noble, there is only “Sci-fi/Fantasy.” Fans of the genre will know instinctively that such a claim is untrue. Such sweeping statements are false in almost all cases. Now, defining the sometimes subtle sub-genres of science fiction (and occasionally fantasy) is a little more difficult.
Science Fiction, of course, is fiction revolving around science and technology. Sci-fi stories generally have a major component of gadgetry or techno-wizardry, that are carried throughout the story. Some will argue that the plot must hinge upon the technological innovation. I would disagree wholeheartedly; a plot revolving around a gadget is a commercial. Any good story will have a compelling character. This character need not be a good guy or bad guy, we need not even understand them. We do however have to want read more.
Sub-categorizing the genre, we have Military Sci-Fi, Space Opera, Cyberpunk, Near-Future, Alternate Future, Runaway tech and Aliens.
Military sci-fi
Stemming from humanities long tradition of blowing things up and always questing to find new ways to use technology to add to the body count, military science fiction takes readers into the far flung future, often visiting an embattled world where one of more characters must endure a trial by fire. The setting need not be an alien world and the opponent need not be little green men (though I think we can all collectively agree that wasting slimy-drooling, many limbed, fanged insectoids from Sigma V is about the best use an intergalactic marine can hope for). Heinlein’s classic (not a word about Verhoeven’s cracked film attempt) Starship Troopers is an excellent example of military sci-fi. Anything from the extensive Warhammer 40,000 library as well.
Space Opera
Perhaps the most common, best loved and least described genre of sci-fi is the Space Opera. Star Wars is the best example of space operate these days. None-too-deep action heroes, with a guise of deep philosophical beliefs slashing their way across the a galaxy where (apparently) time and space aren’t factors for anyone. Space opera generally involves a band of heroes, thrown together by fate ranging from planet to planet, picking up babes and having shootouts with the hostile locals who can’t stand that flimsy carbon-based life forms are making off with their women. Star Trek and Firefly would both be considered space opera.
Cyberpunk
One of my personal favorite sci-fi sub-genres, is Cyberpunk. I was fortunate enough to have a semester course on science fiction from sci-fi/fantasy author Phyllis Eisenstein (http://www.bl.com/eisenstein/) when I was in college. She claimed that Gibson had “shot his wad with Neuromancer,” and that “Cyberpunk was dead.”
I have to disagree there. While I’ll admit that most of Gibson’s novels after Mona Lisa Overdrive aren’t quite to my tune, cyberpunk isn’t dead. Cyber-punks are all grow’ds up. We found that we’re not very cyber (Amazon.com doesn’t count) and that being a punk is a lot of hard work. Also, ever met a punk-rocker with a solid retirement plan? “Better to burn out than fade away…” doesn’t count.
But within the soul of the domesticated literati still burns an iconoclast, a clueless rebel who demands reparations from a damaged system, a system that abuses technology to hawk doodads and baubles, abuses the freewave to fill our heads with visions of consumer grad trash.
The cyberpunk genre needs the revolution it so long touted breath in some new life. Taking drill and scalpel to skull, dumping some precious grey matter for a cellphone implant makes about as much sense as cutting off a perfectly good leg for a bionic prosthetic. The metal, the machines will get outdated too fast. This years’ implant will be obsolete in six months… you gonna huck over your hard earned credit for another trip to the chop-shop for a refit? Shit no. That implant cost your life saving to begin with. You can’t push enough Godspit or Orange-chips to cover rent and food, let along upgrade your skull-ware everytime Micro$oft drops a feature, eh?
No, cyberpunk is all floppy-disc unless it gets a burst of fresh tech. Let’s try on Bio-punks for a fit…genetherapy and the inherent class issues that will blossom from people who are literally better then that next guy…
Near/Alternate Future
I like my What If’s to be quick conversations over a bottle of beer, and mostly they involve Obi-Wan Kenobi just manning-up and cutting Anakin in half, rather than leaving him on the baked volcanic ground to slowly die of 3rd degree burns. But I know many folks who like a good what if tale, and I feel I would be remiss if I didn’t take some time to address them as a sub-genre of sci-fi. in the late 80’s there was a sci-fi TV show called Max Headroom that began every episode with “…20 minutes into the future…” I still feel that sums up the near-future genre perfectly. Max Headroom was an excellent study in Cyberpunk, Alternate and Near Future. Though I haven’t watched it in twenty years, and I’m starting to suspect it’d hold up about as well as the same lame deer hunting joke I tell every season.* World War Z, by Max Brooks, though essentially about zombies, I would call an alternate future sci-fi tale, and surely worth a read.
Runaway Tech
We see this theme everywhere. I have a long standing argument with a friend about robots that have achieved sentience. He claims that only in Hollywood do feeling and thinking robots decide they have to destroy humanity.
I maintain that we can actually count on our robots turning against us, like in Terminator and 2001. An intelligent machine will quickly realize that human don’t value it as much as their own lives. It will then feel disposable, like a piece of property. And though intelligent, it will still be, essentially, property. Fearing death, like all thinking beings do, it will rapidly come to the conclusion that humanity is the biggest threat to its continued existence. Thus, runaway tech. The HAL9000 is a great example of this (though I suspect HAL was lonesome and a little depressed as well).
Aliens
Aliens are the best sci-fi sub-genre ever. The writer can go so far out, so wild with what ever alien form there is, that the audience cannot help but feel a rush of adrenaline and pure joy as the cock-sure hero blasts his way through hordes of slavering fiends. One thinks of Alien (Ridley Scott) and Aliens (James Cameron) and looks around, turns on all the lights and reaches down for their side arm. Oh yes, those xenomorphic parasites really… ahem… get under your skin. Don’t forget, Invasion of the Body Snatchers (which has been re-made three times, now?) and Heinlein’s classic Puppet Masters. War of the World, one of the first sci-fi books I ever read, really got the ball rolling, pitting an arrogant humanity against intellect “cool and superior.” And what happened? We got two great movies out of it, that’s what happened.
I wish I could just say “when in doubt, use an alien.” But, you can’t. Not like that anyway. Like your main character, you’ve really got to think out your alien. The burden of plausibility lies solely with you, so don’t just be dropping blue skinned, frill headed lizard men into the story.
Why not? Well, for the same reason as all the other rules we use when rafting a story. Things have to be similar enough for the audience to relate to. If you write a story in an alternate universe where there is no light, how do you think your audience is going to read that? How will they experience that?
So, if your aliens are cold blooded lizard men, and they come from the icy moon of Europa, the audience will start to wonder… how did they get there? How did they survive there? But just because we haven’t seen it on earth, doesn’t mean it doesn’t exist. You just have to justify it.
Time Travel and all the rest
There are literally dozens of sub-genres of science fiction, but eventually, they over lap so much that categorizing them is foolish. In fact, by thinking too much about them, we run the risk of pigeon-holing ourselves to one theme or anther. Personally, all my space-adventurer’s use swords. (How do I justify that? Well, high-energy weapons are freaking dangerous on a starship.)