The Dispossessed

Have you explored any Ursula Le Guin or Kim Stanley Robinson yet? You might start with The Dispossessed

I'd recommend Left Hand of Darkness or The Dispossessed for more "classic" sci (other planets, space trave), or The Lathe Of Heaven for a story that's totally standalone and starts off in a more normal Earth. Beautiful prose, makes you think.

No particular order: East of Eden, The Dispossessed, The Lord of the Rings, Giovanni's Room, Stoner.

Ursula Le Guin - The Dispossessed. Literary sci-fi exploring freedom, anarchism, ambition and responsibilities.

and in SF the Dispossessed

The Dispossessed, Le Guin - with the engineering background, this is the one where the physics is doing structural work rather than atmosphere.

Honestly, most of my favorite books are standalones: - Jonathan Strange and Mr Norrell - Small Gods - I Who Have Never Known Men - Vita Nostra (there are sequels but they can be skipped) - The Last Unicorn - The Dispossessed

If you want books that force you to build your own mental muscles rather than handing you a list of rules, you should look for stories and essays that offer no easy answers: The Dispossessed by Ursula K. Le Guin

If you're looking for inspiring fiction you might try The Dispossessed by Ursula K Le Guin