Quick and to the point, Isolation tells the story of Heron (who we met briefly in Partials) during the Isolation War. It gives a better picture into the Partials: how they are made, how they are trained, and why they might not only want to, but even been the right to, kill us.
It’s a good story and I hope to see more of Heron in the second and third books of the Partials Sequence. It’ll be interesting to see how she’s grown and changed in the intervening years and how she interacts with the other human (and not) protagonists.