I love the “Big Dumb Object” trope that Reynolds uses here. It just seems so… possible. That something we don’t understand is out there, waiting for us to find it. Some almost unfathomable relic of an alien civilisation. I think Reynolds uses that trope pretty well in Troika: it’s a neatly executed little novella, with a good twist at the end. It may not seem much to look at — it’s quite a slim volume — but Alastair Reynolds writes well, and the structure is well-executed (much as I usually dislike stories where you go back and forth between past and present).
I’m not sure why Reynolds chose the idea of a Second Soviet to frame the story, but it worked well for me. It was a bit of a shock to go from the vague idea that this was Soviet Russia — the first Soviet Russia — to realising that this is a later Russia, post-internet, post-freedom.
I didn’t get the strongly pro-space travel vibes from this that other reviewers seem to have done. To me, the situation in Russia overshadowed the possible touches of commentary on that. If anything, there was maybe a criticism of using space as a means to an end (political, to show superiority, etc) rather than as an end in itself.