Sure the engine tech is fantastical, but the "realism" is in the attention paid to g-loading, momentum, the vast expanse (heh) of space, etc. The authors have c

Sure the engine tech is fantastical, but the "realism" is in the attention paid to g-loading, momentum, the vast expanse (heh) of space, etc. The authors have chosen strategically which aspects of their story to be fantastical and which parts to keep hard. And of course, every good sci-fi has to do this. Which is why I personally like the metric of "does part of the enjoyment of this story come from a (somewhat) realistic portrayal of real science". Conveniently categorized by my non-sciencey reading buddy. The more it does this, the "harder" it is. However that means the location of the fuzzy boundary is subjective, but we can probably rank different stories relative to each other. The Martian is harder than The Expanse is hard than Star Wars. Pretty clear I'd say. The Expanse may have unrealistic engine tech, but at least the spaceships aren't dogfighting Second World War style.