If you like military scifi, I highly recommend Heinlein’s “Starship Troopers” and “The Moon is a Harsh Mistress” by the same author. “The Forever War” by Joe Haldeman is also solid. Be careful which version you read, as it’s been edited quite a bit: https://en.wikipedia.org/wiki/The_Forever_War I read those in the last year, so they are pretty fresh recommends.
I also really liked “The Stars My Destination” by Alfred Bester. It’s a very tightly plotted scifi novel from the 50s. If you want to read more pulpy crime/scifi, I really liked “Junkie” by William S. Burroughs, and of course “Naked Lunch”, “The Soft Machine”, “Nova Express” and the “Ticket that Exploded” by the same author. All very much a challenge to read, but they throw up phrases and images that will stay with you forever.
For psychological scifi, I really like JG Ballard’s work. Some of his work is more experimental, but it all feels very current, even if he began writing in the 50s. His life story is easily the most interesting bit of his work.
Further into the cyberpunk/word salad genre, “Neuromancer”, “Mona Lisa Overdrive” and “Count Zero” are at least semi-decent. They are laughably dated, and written on a typewriter, but still radiate cool. Of those, Neuromancer is head-and-shoulders above the others.
If you want to go a bit further afield into Eastern European scifi, I highly recommend “Roadside Picnic” by the Strugatsky brothers. A very dark adventure story from the 1970s about the aftermath of an abstract alien visitation, and the effect it has on the “stalkers” who recover objects from the Visitation Zones. Also made into a film called Stalker, and a the loose basis for the game S.T.A.L.K.E.R.
“We” by Yevgeny Zamyatin is a decent read if you like dystopian novels, it influenced many in the 20th century. I’m not entirely sold that it’s a great novel however. If you like Doctor Strangelove, read “Memoirs found in a Bathtub” by Stanislav Lem. If I think of more scifi novels, I’ll let you know.
I’ll do literary fiction next maybe. I define literary fiction as “anything not scifi/fantasy”.
I’m pretty divided on ancient Rome to ancient Greece. That period of 600-400AD of Athenian Greece is amazing. But Rome had such interesting stories and insights. If it tips me over into the Roman camp, I have 28mm Legionnaire models and fight my friend’s Celts in historical wargames.
I don’t really have strong feelings on Rebels v Empire – I would prefer to live in the Rebel section post-war. But I don’t like Jedi as anything other than space knights. While the Empire have snazzy uniforms, I’d hate to pay the taxes required to fund the military.
I’ve never finished Dune, I’ve tried 3 or 4 times, but find the prose too stilted. It’s a shame, as it’s really influential on 40k. I think it’s had so much sucked from it over the years by other works, it’s nothing but a dry husk.
I mostly read books to feel stuff.