It’s amazing, but has one big gotcha.
You don’t even need to upgrade your existing sub-light engines. Just run Prolog fuel through whatever you’ve got, and you’ll have FTL capability.
With Prolog FTL, just tell your spaceship where you want to end up, and Prolog will figure out how to get you there, piloting your course via wormholes through hyperspace.
How does it work? Prolog fuel is a smart fluid. It establishes a quantum superposition of your existing engines across multiple universes. Your spaceship takes every possible route, then selects only the outcome where you arrive at your specified destination.
Don’t worry, Prolog does the thinking for you. You don’t have to understand anything else about it.
Well—unless—that is to say, by default, sometimes you’ll come out in a universe that sits on a totally different timeline. You’ll be there, but the rest of reality might not be what you expect. Or sometimes you’ll arrive in the same timeline, but a million years after you left.
If you don’t want that to happen, then, I’m afraid, you will have to study Prolog in a little more detail. First you’ll have to master your sub-light engines at the level of a senior flight engineer: you should be able to build, from parts, a working sub-light space drive. After that, you’ll need one PhD in quantum mechanics, and another PhD in quantum computing. Then you’ll be able to come out anywhere you want, and in the same universe, and at the right time.
That little detail aside, isn’t Prolog great?