I haven't read the novel, but going by the Wikipedia article you could argue that just because it features astronauts on the ISS doesn't yet make it science fiction - as long as nothing unusual happens to the astronauts, what goes on on the ISS is no more science fiction than what an airline pilot does in their day-to-day job.

Even the author seems to agree (also from Wikipedia): "In an interview, Harvey stated that her goal was to write the novel as a "space pastoral", focusing on realism and the beauty of space rather than the speculative nature of science fiction."