"The Doomed City" is one of the best pieces of philosophical scifi I've ever read:
"Hard to be a God", mentioned below, is a better example. Soviet era Sci-Fi where Star Trek esque space communists try to uplift a medieval society into modern political belief before establishing official first contact.
People literally wake up in The Doomed City when the pandemic has started in 2020, for example.
I consider The Waves Extinguish the Wind their best novel, for its simplicity. But I didn't read any English translation, and it's a big "but".
Agreed about the melancholy.
it's as upbeat as the title suggests.
1. https://www.npr.org/2015/03/19/392634682/mountaineer-is-a-mu...
Worth noting that a video game [2] based on the novel (which looks very well produced) is releasing in November.
For a more recent take on a similar theme, see also „Blindsight“ by Peter Watts.
Others are suggesting Hard to Be a God by the same authors, which is an okay book, but it's not really SF as most people think of SF IMO.
As well as the Roadside picknick, the Doomed city, A billion years before the end of the world, the Ugly swans, etc etc - really most of their books - it’s a good literature and not a sf in its usual sense.