My two personal GOATs are A Fire Upon the Deep and A Deepness in the Sky by Vernor Vinge. Both won Hugos, so they shouldn’t be tough to find.

To give the quick pitch without spoilers, they’re hard scifi space operas, but heavily character-driven and focused on a high degree of grounded physical realism. On top of being a competent writer, the author (recently deceased) was an active compsci and math professor, so the books have this wonderful feeling of rootedness — in that the technology reflects creations that humans might realistically invent in the next few centuries if we don’t nuke ourselves up first. Also captures the vibe of how we ordinary humans would react and adapt to the consequences of our future tech.

It’s the fun adventure-narrative of Star Wars Episode 4 blended with the political intrigue and attention to space physics that The Expanse series leans into.

Might already be on your radar, but I’ll also toss out Vonnegut as a great choice for soft scifi… ignoring Timequake.