When I speak of power chords in the context of fantastic literature, I’m talking about certain classic tropes that have the visceral punch of heavy musical riffs: blaster guns, spaceships, time machines, aliens, telepathy, flying saucers, warped space, faster-than-light travel, immersive virtual reality, clones, robots, teleportation, alien-controlled pod people, endless shrinking, the shattering of planet Earth, intelligent goo, antigravity, starships, ecodisaster, pleasure-center zappers, alternate universes, nanomachines, mind viruses, higher dimensions, a cosmic computation that generates our reality, and, of course, the attack of the giant ants.