Not necessarily pro-socialist or anti-capitalist, but I just finished Fahrenheit 451, and it was a good antifascist book. It’s short and a great read.

Octavia Butler is great. Parable of the Sower is a good distopian story about climate apocalypse, late stage capitalism, and dialectics. Kindred is also great. Wild seed was ok but not as good as the others. I can’t speak for the rest of her writing, but I’m sure it’s great.

I’ve heard Thomas Pynchon is good, and he’s good at para political metaphors and such.

Here’s my list of fiction I need to read if you want more:

Some of these have already been mentioned but I would suggest the following:

• What Is To Be Done by Chernyshevsky. Lenin read it five times in a summer and named his pamphlet after that. Xi Jinping lists it as a fave too. It was huge in the years leading up to the October Revolution. It has better credentials as revolutionary socialist literature than probably anything else. It is a cozy read, and i think the narrator is funny.
• The Dispossessed by Le Guin. Yeah it is anarchist, but i think it’s interesting how she explores both liberalism and anarchism, and imagines how things like language change when your mode of production do. I have a twitter thread on some highlights/questions it explores (spoilers though).
• Babel by RF Kuang. This is not socialist, IMO, and its anti-capitalism is more anti-imperialism rather than taking the form of moving past capitalism. Still it’s a fun read; the world building replaces mechanization with magic, and explores how industrialization/capitalism leads to imperialism (eg Opium Wars). I have a thread on some of the world-building in it and why it’s neat from a socialist angle here (again, some spoilers).

I did read The Jungle too, but i thought it was kinda dated, miserable and uninspiring. Maybe you like it better than I did.

Pretty much all of Vonnegut’s stuff is very pro-worker and very anti-capitalist. His novel Jailbird covers a fictionalised version of the Pullman Strike, Player Piano deals with automation and how it can negatively impact the worker, Slaughterhouse-five is (among many, many other things) anti-war. God Bless You, Mr. Rosewater concerns the class system and all its flaws. Hell, he dedicated Hocus Pocus to Debs. Plus, he was a fucking fantastic author to boot.

I’m going to start reading the dispossessed after having read Dan Simons’ Hyperion cantos. I read “the ones who walk away from omelas”, a nice and very short story, as a sort of appetizer for the book and I’m quite excited

Ursula K LeGuin was anticapitalist and wrote books to match, often beautiful ones that recognize the complexity and variation of humanity. I’ll always recommend this short story, which you can read for free right now if you’d like. This particular story is the opposite of explicit, though - it’s a complex mix of metaphor and human connection. She does have other much more explicit works, though, like The Dispossessed.

The Jungle was explicitly and viscerally anticapitalist.

There are also many historical fiction books set during socialist revolutions.

I wouldn’t say that it is explicitly Anti-Capitalist/Pro-Socialist, but the Wiedźmin (Witcher for the anglos) book series has some pretty cool anti-imperialist vibes in it. It is actually extremely different in politics to the games by CDPR and is generally better than most Euro fantasy in its treatment of racism and nationalism. I think the author has some anti-soviet vibes, which didn’t matter that much to me at the time of reading, but I guess are worthy of note for many here. Books are on libgen in many languages, and the audiobook versions by Peter Kenny are very well acted.

I also haven’t gotten around to finishing Chernyshevsky’s “What is to be done” (not the Lenin one) but I liked it so far. It has also been a while, but Ramos’s Vidas Secas was one of my favourite books as a child, but only recently I learned he was communist. Not sure how that last one translates to English though.

Also since you mentioned Animal Farm, I’ve head that “Brave New World” is generally regarded as an “opposite day 1984”. Can’t attest for its quality though, as I haven’t read it yet.

Also Neal Stephenson has weird thoughts and I wouldn’t consider him a socialist, and his books kinda read like having a bad trip while reading historical conspiracy theories, but Diamond Age kinda has a “broken clock correct twice” aspect to it. Kinda like the “Cocaine-phase Stephen King” of sci-fi.