Originally from https://fantasticmetropolis.com/i/50socialist/full/
This is not a list of the “best” fantasy or SF. There are huge numbers of superb works not on the list. Those below are chosen not just because of their quality—which though mostly good, is variable—but because the politics they embed (deliberately or not) are of particular interest to socialists. Of course, other works—by the same or other writers—could have been chosen: disagreement and alternative suggestions are welcomed. I change my own mind hour to hour on this anyway.
Iain M. Banks—Use of Weapons (1990)
Edward Bellamy—Looking Backward, 2000–1887 (1888)
Alexander Bogdanov—The Red Star: A Utopia (1908; trans. 1984)
Emma Bull & Steven Brust—Freedom & Necessity (1997) 
Mikhail Bulgakov—The Master and Margarita (1938; trans. 1967)
Katherine Burdekin (aka “Murray Constantine”)—Swastika Night (1937)
Octavia Butler—Survivor (1978)
Philip K. Dick—A Scanner Darkly (1977)
Thomas Disch—The Priest (1994)
Gordon Eklund—All Times Possible(1974)
Claude Farrère—Useless Hands (1920; trans. 1926)
Jane Gaskell—Strange Evil (1957)
Mary Gentle—Rats and Gargoyles (1990)
Lisa Goldstein—The Dream Years (1985)
M. John Harrison—Viriconium Nights (1984)
Ursula K. Le Guin—The Dispossessed: An Ambiguous Utopia (1974)
Michael Moorcock—Hawkmoon (1967–77, reprinted in one edition 1992)
Mack Reynolds—Lagrange Five (1979)
Keith Roberts—Pavane (1968)
Lucius Shepard—Life During Wartime (1987)
Norman Spinrad—The Iron Dream (1972)
Michael Swanwick—The Iron Dragon’s Daughter (1993)
Jonathan Swift—Gulliver’s Travels (1726)
Alexei Tolstoy—Aelita (1922; trans. 1957)
Ian Watson—Slow Birds (1985)
H.G. Wells—The Island of Dr Moreau (1896)
E. L. White—“Lukundoo” (1927)
Oscar Wilde—The Happy Prince and Other Stories (1888)
Gene Wolfe—The Fifth Head of Cerberus (1972)
Yevgeny Zamyatin—We (1920; trans. 1924)
I see Mieville retains his SWP views, We was the first novel banned in the USSR possibly first book if you don't include pamphlets from political groups, and his career was effectively ended by its publication abroad. He had to apply for exile to Stalin in 1931 to be able to write again. A bit more serious than "semi-official unease".
It didn't get past the censors, it wasn't published in the USSR until 67 despite being written in the late 20s. And that publication was heavily censored, Bulgakov had written and burnt the manuscript several times over decades to avoid arrest. The "complete" version was published after his death in France as a Samizdat publication.
Reddebrek
According to the introduction from the Broadview Press edition of the book, We was only officially banned in the USSR in 1924 (Zamyatin tried to publish it already in 1921 but none of the Soviet publishers wanted to take it on, which is why he reached out to publishers in the West instead). Same source says Zamyatin was briefly detained in 1923, but it wasn't until 1929, during one of the first purges of the All-Russian Union of Writers (of which Zamyatin was a leading member in Leningrad), that he was officially condemned and all his works and not just We were banned.
So although I've seen this "first novel banned in the USSR" epitaph attached to it in other places, it's interesting if it's actually true (I'd be pleasantly surprised if no books had been banned before 1924!).
Thanks Jon and reddebrek.
Could also add Robert Heinlein's Logic of Empire, which explains how to use economics to make people into slaves (as in indentured servants, company stores, scrip etc )
Salt by Adam Roberts.
I think this is a pretty sloppy list, as befits something thrown together by someone whose books are (if you ask me) all unreadable, aside from the excellent The City and the City. Aside from some of the choices themselves, it was curious to see The Rival Rigelians described as 'explicitly examin[ing] the relation between capitalism and Stalinism' (it does no such thing, explicity or otherwise, and is deathly boring to boot); and of Anarres as 'high-tech'.
Three books that would belong on a proper list (an updated one) are The Final Conflict, which can downloaded directly from libcom: https://libcom.org/library/last-conflict ; Hogan's Voyage from Yesteryear; and Doctorow's Walkaway.
Matiasz's 1% Free is reviewed on this site -- https://libcom.org/blog/review-1-free-maximumrocknroll-political-columnists-sci-fi-novel-31122016 -- but I am in the middle of the book, have not read the (presumably positive) review, and have nothing to say on the subject.
I was going to add Adam Roberts' Salt, but Serge Forward has beat me to the punch by a day. For those interested in knowing, the content is something to this effect as I recall:
Sixteen 'nations' (communities) set out from Earth (probably not ours) to settle a planet that was wrongly identified as being much more conducive to human inhabitation than it turns out to be.
Among the sixteen nations, one is highly monetarised (electoral system: you have as many votes as you pay for!), class-and-personally-hierarchic, and patriarchic. Another -- which entered the entourage through subterfuge -- is anarcho-communist. (Aside from 'hierarchic' -- used as term of abuse by the one side, and 'anarchist' -- used as term of abuse by the other -- there is little or no political language in the book.)
The two sides come into armed conflict.
The story, aside from the last chapter, is a series of accounts in chronological order told respectively by the leader of the propertarian side, and by the chief protagonist on the communist side. (This latter is no ideal person.)
Sometimes it's very funny.
I've only read We and Atlas Shrugged on this list. Which of these books should I tear into first? Almost all the science fiction I've read has been Harlan Ellison.
I'd recommend LeGuin's The Dispossessed: An Ambiguous Utopia for a light and interesting read. If you're into hard sci-fi, Robinson's Mars Trilogy is great (though be prepared for reading pages-long description of Martian geology, terraforming tech and techniques etc.).
Continuing from my post above, three more comments:
1) Another book fitting the description 'socialist science-fiction' is Wage Slave's Escape by (ex-)IWW member Mike Ballard (of Australia): https://www.amazon.com/Wage-Slaves-Escape-Michael-Ballard/dp/1312810971
2) Usually neglected, and unsurprisingly not mentioned by Mieville either, is Bellamy's second book: a decade after Looking Backward, he wrote Equality, which was so different from the first one that it was praised by Kropotkin*. (The book is without 'the industrial army' etc.) Equality can be read here: https://www.gutenberg.org/ebooks/7303
No doubt unaware that News from Nowhere was written against Looking Backward, Bellamy wrote a positive review of Morris' book (while questioning the absence of description of 'system' and 'administration' in the story's society) : https://www.marxists.org/reference/archive/bellamy-ed/works/1891/morris-news.htm .
sequence:
Bellamy's Looking Backward:1888
Morris' News from Nowhere: 1890
Bellamy's review of News from Nowhere: 1891
Bellamy's Equality: 1897
* Kropotkin quoted on this on page 191 of Patai: Looking Backward, 1988-1888 : Essays on Edward Bellamy, which can be seen here: https://archive.org/details/lookingbackward10000unse/page/190/mode/2up?q=Kropotkin
3) Matiasz's' 1% Free is in my view without any merit.
In the way of socialist/communist science-fiction, two authors whose book I have not mentioned (because I have not personally read them) are Arkady-and-Boris Strugatsky, and Ivan Yefremov.
See here: https://www.worldsocialism.org/spgb/socialist-standard/2020s/2021/no-1405-september-2021/sci-fi-utopias-and-socialism