Our main (but not only) point-of-view is Rosemary Harper, a human born on Mars fleeing her old life under a new identity. She joins the eccentric and multi-racial crew of the Wayfarer, a contract ship that builds "sublayer" tunnels between different places in the galaxy.
The book is essentially a spaceship adventure story that I found somewhat reminiscent of Robert Heinlein (if he'd been a lot more liberal). That said, it has a quality that's frequently lacking in the world(-building) of science fiction: it's well written. Chambers' characters are likeable, consistent, and well thought out. The Wayfarer's first job after Rosemary joins them is short - an opportunity to introduce us to the characters and their behaviours, and the physics of the work the Wayfarer does. We then get into the meat of the story, with a new and lucrative contract locking them in to a voyage of over a year. On the trip, they encounter pirates, family, multiple types of aliens (some hostile), and friends. As I said, a spaceship adventure story. But Chambers' main themes revolve around friends and family and consenting sapients (not just consenting adults) - that's what this book was mostly about.
I thought the biggest mis-step in the book was a very late stage switch to Corbin's point of view. Prior to that POV switch, Corbin had been built up for the entire book as a necessary asshole that no one on the crew liked. And suddenly we're thrown inside his head as he's imprisoned and beaten (this is arguably a spoiler, but you won't see it coming - however, it does mostly make sense later). Dear author: if you're not willing to go with his POV when he's an unrepentant asshole, it's a bit of a cop-out to switch so late in the book and say "be sympathetic to this character now."
A short excerpt from the sequel that's provided as a teaser at the end of the book makes it clear that friends, families (and probably consenting sapients) are the themes she continues to pursue: I think I've had enough. Don't get me wrong: I really enjoyed the book and got through it faster than any book I've read in years. But I felt like this was enough of her very specific style and philosophy.