- Stargate on archive.org (1976)
The "Gate" could open the way to distant galaxies—
or destroy the whole Universe…!
Saw the cover in a tumblr SF feed, and the title and summary caught my eye.
Despite the year, it's a pretty current story of corporate engineering management. The engineer, Robert Collins (a newbie in way over his skill level), and the company "lawyer"/gun thug/investigator Scarlyn Smith (basically Mike from Breaking Bad), try to figure out why the former chief engineer Norton was vanished from his funeral and turns up in pieces throughout LA. Collins manages to spare time from playing detective to do his job and build the Gate…
Spoiler discussion hereafter.
So the "one fictional science idea" of this book is a matter transporter. Originally somewhat short-ranged, but it allows you to build: Instant teleports across the world, or up to orbit (how conservation of motion is handled is not addressed; jumping to a space station moving 100x faster than the surface should plaster your bits on the wall), or to make a drone ship move FTL by transporting itself forward over and over (apparently biology can't handle the slight deviations in many ports, but electrically-driven starships can).
The Gate is just a giant transporter, with a reach measured in thousands of light years. In its first operational test it targets Tau Ceti, 12 light years away, and rips an asteroid-sized chunk of matter from a planet, including plant life. There's a few sentences about Collins having moral qualms about this. The villain's plan is rather more ambitious, but insane.
Even with just the "normal" application, this is a horrific device. Interstellar war? Just tear the enemy's planet apart from the comfort of your own orbit. You can use it to instantly travel across the Galaxy, or… the plot has another application for it.
There's an adage from Larry Niven's Known Space series, the efficiency of a star drive is directly proportional to its value as a weapon; there meaning that fusion drives, laser sail launchers, and interstellar laser comms make weapons as good as any main cannon. But this is far beyond that. Instant travel means you can kill a planet or a solar system instantly.
Not a particularly well-written or interesting book as literature, but piecing together the dangers of this thing, especially from the crazy scientist who shouts about "the crab!", gives it more value.