Merlin's Snake Oil, that is the magical or SF'nal elements, is the not-so secret fuel of SF&F literature.

This is the trick behind good milieu novels like Lord of the Rings, and Jack McDevit's far future thrillers and mysteries. It's what makes Edgar Rice Burroughs' otherwise dated Mars and Venus series compelling – we experience the Other because the hero spends each novel fighting or making love to it.

On the other hand, Merlin's Snake Oil keeps interesting stories afloat. George RR Martin's and Guy Gavriel Kay tales of mighty princes would break a historical setting, but flourish like algae on a pool of the sorcerer's gloop. Mary Sue does the Cathar Chateau de Roissy needed a quasi medieval world with a kink. And Weber's modern people like us refight the Napoleonic Wars could only work in space.

These work best when the oil is not so much a plot device, as a plot steroid. War of any kind is lethal enough, but in Weber's Honorverse, bomb pumped nuclear lasers can wipe out a thousand ship's crew in just a handful of words. George RR Martin's sinister cloud on the horizon is so much more sinister for being magical.

So, no matter why the author introduces Merlin's Snake Oil, it's most effective if allowed to flow through the entire story, wowing the readers whenever they turn the corner, and pumping up the plot to so that the themes sing like a greatsword when it sweeps aside another blade.

All this suggests to me that you can work backwards from central myth –the level of "Boy finds girl, boy loses girl..." – to a good SF&F story by using the fantastic fluid to turn the mundane into the archetypal.

Take, just for example, an entirely hypothetical multi-threaded noir spy novel set in a far future of space stations and rocket ships.

When I think about classic – mundane - espionage tales, I think of high stakes and horrible personal peril. So, my instinct would be to blow up a planet, and make a likable character suffer an ingenious but toe curling violation - stakes and peril that only SF can serve up. And I'd have those possibilities driving at least some of the plot.

There's also the spy's loss of identity – didn't William Gibson had a spy discover she was a policewoman with a personality overlay, only the overlay liked the status quo?

What else? Spy writers love cosmopolitan cities like Istanbul. How about the ultimate cosmopolitan city – perhaps a space station of a thousand cultures, and as many languages and currencies?

And while we're on culture, why not use Merlin's Snake Oil to float some humans so far from the norm as to be almost literal aliens?

None of this would require extrapolative SF. The technobabble is still technobabble, even if it's extrapolated by Nobel Lauriates*. The reader's thrill would be in getting drunk on Merlin's Snake Oil and riding the hero's shoulder as he battles a cyborg on the decks of a burning spaceship as it spirals through the atmosphere of an overpopulated world, its hold promising nano-wibble-death to the inhabitants.

Just saying...