I think this sequel to Fonda Lee's Exo is better than her first book, despite a somewhat slow start. The Zhree decide that Earth is too far away and costly to manage, and decide to abandon the planet, seeking to rescue 90,000 inhabitants to preserve the human species, with a focus on the hardened Exo's. Meanwhile, tensions among the core humans are led by rebel groups called Sapience and True Sapience. We continue to watch events develop through Donovan Reyes, the son of the former Prime Liaison. Donovan wants to stem the violence by capturing the leaders, who are both close to his squishie (human) friend, Anya. Everything changes when the Rii invade and the Zhree agree to surrender the planet to their nemeses, who will kill off and/or enslave humanity, forcing Donovan to seek help from Sapience to disable the failsafe mechanism, making Exo's unable to defend themselves against the Zhree. Action packed story of pack loyalty and honor: 4.5 stars. ( )