Arthur C Clarke famously once wrote that "Any sufficiently advanced technology is indistinguishable from magic", and this story is the living embodiment of that, presenting the idea from both perspectives. I enjoyed how the book regularly switched between those perspectives, showing how conversations were perceived differently by the protagonist who controls the technology and his more primitive, magic-fearing counterpart. The struggle to communicate is one of the themes of the book.
Besides that, this is a book that also tries to deal with the concepts of loneliness and isolation, and the profound depression that can spring from this. I found it interesting that the book depicts a technological solution to these human problems, but one that is deeply flawed.
Overall, I enjoyed the book a lot. It's not action-packed, nor is it full of intrigue or plot twists; it prefers to focus instead on the thoughts and feelings of the two main characters. I didn't find it as gripping as some of Tchaikovsky's other work (e.g., his excellent Children Of Time series), but it was a thought-provoking and very worthwhile read nonetheless.