This book is kind of speculative Sci-fi, in that it's all about "what would it really be like to live long-term in space?". It's about the Fleet, which is the large exodus ships from Earth, that have now been in space for centuries, and while they DID get people off of Earth, they aren't really going anywhere. They found that a lot of other species exist, and a lot of other already fully developed planets and societies exist, so humans aren't exactly pioneering space travel or planet colonization. Lots of people from the fleet leave to live elsewhere, but it's not like they found another empty Earth for themselves.
Instead, they find themselves a technologically impoverished race that was only rescued by help from the coalition of other sentient cultures, and while they are reasonably sufficient in the fleet for food and clothing and so on, they don't have a planet, and they have no exports that anyone else wants. The only way to earn credits that can be spent on products outside of the fleet is to go live somewhere else, so often, people do.
That's mostly what this book explores, through various characters. What it means to be living on a somewhat stagnant colony, with no real exploration goals, just endlessly recycling resources.
It tends to look at relationships, the meaning of family and the feeling of belonging, and what a life means when it isn't being driven forward, but mostly maintaining. What it means for a culture that isn't at war, or in a position to dominate others, but is allowed just to exist as itself.
There is no "bad guy", no war, no horrible crisis to overcome, no "chosen one", no laser battles in space, just a very good book about a pretty believable scenario of what normal life might be like.
I really like Becky Chambers so far, and I'm very excited that she is a fairly young writer at the beginning of her career. I'm looking forward to what she has to say.