Disclaimer: Just an arm-chair Space Engineers player here.

> I always thought that was a very well thought out aspect of The Expanse: spend half the trip accelerating, then flip the ship around and spend the other half slowing down (aka accelerating in the opposite direction).

With current technology you would not do this, since that means using extra fuel that weighs a lot and thus increases the force required for the same amount of acceleration as you'd get with less fuel and less burn.

Of course that changes drastically if the fuel required for more acceleration (and its container) is very light-weight. I would assume fusion or fission based thrusters would be better in this regard, however I think currently those produce very little acceleration in a vacuum compared to combustion thrusters.

Any impulse / reaction engine is subject to the Tsiolkovsky rocket equation. It's just that with higher specific impulse and reactant velocity the total mass is reduced.

Since the rocket equation is a function of the effective velocity times the natural log of the wet/dry mass ratio, changes in exhaust velocity matter more than changes in propellant mass: you're better off with heavier propellant moving faster, than lighter propellant moving slower.

Ion drive engines tend to use xenon (a heavy nobel gas) for this reason. Unfortunately, xenon is rare even on Earth, and extraordinarily rare in space -- tanking up on a road trip would be difficult.