In this story about time travel, making small changes in the past can create a better future. The problem is that different people have different ideas about what makes a future "better." To paint it in broad strokes, our antagonists believe that only a certain group of men should have the power to make decisions about laws, education, bodily autonomy, and so on. Our protagonists disagree, and they have the courage to go into the past and fight for their rights.
The glimpse we get into a future where the cruel, small-minded men win is truly horrifying, but its seeds exist already in our own society. I like what author Ken Liu says in his cover blurb: this story is a "tale of hope in the face of outrage," both within the story and in our own world.
Overall I enjoyed this book quite a lot. I particularly liked the time travel mechanism that Annalee Newitz creates for this story, a set of ancient "natural" machines in several places around the world, of which the origin is unknown and the operation only partially known. The personal story of the main protagonist that's interspersed with her time travels is also very compelling.