I CAN NOT believe this won a Nebula. If you are into romance, you may like this, but if you are looking for a good sci fi, avoid. The great thing about sf is that authors can choose to give their female characters freedom that women don't have in most Earth societies. This main character did not have any agency and she is buffeted around by the romance plot in a very cliche way. I believe the Nebula should go to books that are well-written and exploratory, and this book is neither.
Author did an ok job comparing the lovers to quantum particles in resonance, she obviously has a strong physics background. The last half of the book fell short, though I hadn't read the other books in the series so that might have affected my reading. The last stand-off just plodded along and I didn't get a sense of suspense or the connection between the characters. Once the romance-related conflict was over I was confused why the story was still going on. I cannot see romance/scifi as a viable cross-over unless the romance is a very small part of the story.