This can be anything from Hyperspace in Star Wars, Warp Drive in Star Trek, travel through the Warp in Warhammer 40k or anything else.
I’ve always liked “slow” FTL travel, where going a few light-years still takes a few days or so. I also really like travel through an alternate dimension like in 40k, Event Horizon, Witchspace in Elite Dangerous.
I wanna know your favorite versions, or do you prefer stories that obey the laws of known physics, like the Expanse or Rimworld?
My favourite thing about Halo FTL is how it handles causality, basically relying on the universe to act like a sponge and “soak it up” as it reconciles it across spacetime.
Send too much mass (aka the Halo array) and it massively slows down travel galaxy wide, as the spacetime is “sodden” and takes longer to reconcile it. Meanwhile in the days leading up to the firing of the Halo array slipspace travel suddenly became easier and quicker than had ever been experienced, as the Forerunner realise that after the firing of the array the amount of slipspace travel in the entire galaxy will be nil.
That’s hilarious and deals with half the travel time plot holes - I love it!