Not the person you asked, but I've seen The Expanse described as "hard" sci-fi. It's heavy on space technology, warfare, flight mechanics, things like that. A bit grim and dark at times.

Overall, The Expanse is the single greatest piece of sci-fi that I've ever personally seen. The show is so. Fucking. Good. It's hard to even explain it. The writing, the filming, the pacing, the way they shoot scenes... it's just a marvel to witness.