Fire on the Mountain (1988) by Terry Bison is an alternate history novel that takes place in an African American socialist republic a century after Harriet Tubman’s and John Brown’s successful raid on Harper’s Ferry. I’ve read some of it and have been meaning to finish it. I suppose it’s quite explicit in its socialism, however.

It is not that explicit. It's more one of those family history discovery stories, just the history is alternative and it happens in vaguely socialist solarpunk aesthetics. Honestly, it's worth the reading because there is barely anything else there, but i found it incredibly boring, as the history is given in very small portions which don't even get the clues about many important things, but the mundane slice of life comes in huge chunks inbetween (and i don't like the slice of life).