Basically the title, can anyone recommend some good sci fi books with leftist themes?
People have already justifiably mentioned Iain Banks, but let me throw some more goodies your way.
Kim Stanley Robinson, primarily his Mars series but his other work is great too. In fact, KSR went on Chapo(https://soundcloud.com/chapo-trap-house/bonus-will-interviews-kim-stanley-robinson-with-the-antifada)
Ken MacLeod, who I believe was actually friends with Iain Banks. Check out the Fall Revolution series, or Newton's Wake, or the Execution Channel if you're feeling grim.
China Mieville is primarily a weird fiction and fantasy writer, but he does have an excelent SF book, Embassytown.
Aw hell, throw Ann Leckie in there. Ancillary Justice deserved the praise it got.
I found Ancillary Justice to be a very vanilla space opera, it coulda been published by Baen.
The Culture series by Iain Banks. Pretty wild transhumanist FALGSC stuff centered around a utopian communist society called The Culture, organized by superintelligent AI. It's weird as hell - people can secrete drugs into their brains at will and regularly change their sex, spaceships are sentient, among other things - and it can get real gnarly. Lots of socialist critique of capitalism and imperialism. Start with The Player of Games then Use of Weapons then Consider Phlebas and chronological by publication date from then on for the smoothest introduction.
Mostly conflicts between the Culture and other civilizations. In The Player of Games, for example, the Culture finds itself trying to put an end to a fascist space empire without militarily occupying them.
Since the Culture is post-scarcity, conflicts aren't really driven by resources, but are more ideological or philosophical. So, Surface Detail is about the Culture competing with another society to determine whether they should be allowed to place people in simulated hells as punishment for religious transgressions.
The two traditional starting points are either The Player of Games or Consider Phlebas, with CP being the actual first book, but it's told entirely through the perspective of someone who is actively engaged in a war on the Culture and also hates it, so you don't really get an internal Culture perspective.
The Player of Games is more friendly that way since it lays out what the Culture is like and how it interacts with others.
Not OP, but while I'm not sure I'd consider one of them to be "better" I'd definitely say that Player of Games is a better intro to the setting, as you get to see the Culture proper and how they interact with both themselves and the rest of the universe.
Try The Dispossessed by Ursula La Guin. It's a bit dry but when I was a lib I found the deep dive into how an ancom world would work fascinating.
The Dispossessed by Urusula Leguin and the Mars trilogy by Kim Stanley Robinson.
There are a lot
A very good one I read this is A Memory Called Empire by Arkady Martine. It's about the conflict between the cultural pull of an empire and the threat that empire poses to the cultures in its path. Lots of politicking and intrigue.
Oh shit I read this one. It rules. It's not just a fascinating exploration of imperial power, it's also got the gnarly backalley neurosurgery, refreshingly casual queerness, and polyamory that I crave.
Also by Butler: The Parable of the Sower and The Parable of the Talents are about a young woman's attempt to build a communal society in the middle of a collapsing United States and rising theocracy
Also by Miéville: October, a novel-like retelling of the Bolshevik Revolution
My stock answer to this is the Culture series, it's awesome
I’ve heard good things about The Three Body Problem, a chinese sci-fi series.
It's OK, definitely not my favorite but interesting. Not much of a positive view of socialism, but there's a lot about the ugly side of the Cultural Revolution that made me curious to study more Chinese history. The aliens didn't make a whole lot of sense to me, but maybe that's because they're seen incompletely through a human lens. The writing style was also a little weird and clunky, but maybe something got lost in the translation.
Walkaway by Doctorow is a fun anarcho-communist adventure. Most of his stuff is pretty leftie but not explicitly socialist, especially the short story collection Radicalized
Singularity Sky by Stross is sort of a retelling of the October Revolution but with nanotech and godlike AIs. His work is also mostly vaguely leftie, especially some of his Lovecraftian horror series The Laundry Files, which is partly inspired by Thatcherian austerity
Edit: Doctorow and Stross also wrote Rapture of the Nerds together, which is a silly and weird story about FALGSC. Glasshouse by Stross is also a great mystery/thriller with a FALGSC setting that touches on gender dysphoria and body horror
As a fan of both Charles Stross and Richard k Morgan (of Altered Carbon fame) I was completely surprised to find out that the tech nerd turned out to be a cool lefty, and the guy I thought was cool turned out to be a lib dem
Didn't know that about Morgan, after reading the 3rd book I thought he was more of a revolutionary
IIRC Doctorow was raised by Trotskyites and went through a brief libertarian phase around the dot-com boom, now he's probably a rad-lib
Stross was interviewed on the Trash Future podcast, it's a good one
I also didn't know it, but I followed the guy on Twitter and his takes during the recent elections were, well he's a liberal Democrat voter.
As it happens I was just watching the show, and the earlier comment didn't make quite clear who was who so I did a little digging, and, well, apparently Morgan is worse than just a lib dem... (CW: transphobia)
Oof, that "However"
You'd think that the guy who wrote 3 novels about people switching bodies would have a better understanding of trans people. I'll continue to not pay money for his books
Glad to see Charlie supporting trans rights
Oh I also highly reccomend Fredric Jameson's Archeologies of the future which is a study of different visions of utopia present in socialist science fiction.
Frederik Pohl. The Space Merchants and Jem.
Kim Stanley Robinson. Aside from the Mars trilogy I'd also say his earlier California trio and NYC 2140
Can't speak with authority on this topic at all but the interview with Kim Stanley Robinson with Will and the anti-fada crew was excellent. https://soundcloud.com/chapo-trap-house/bonus-will-interviews-kim-stanley-robinson-with-the-antifada