The First Sister compares itself to The Handmaid's Tale and Red Rising, and it wears its influences on its sleeves, with a lot of overwrought drama in packed into a wartorn inner solar system. The story creaks under the weight of its influences, images mashed together without much sense of coherence, but Lewis manages flashes of talents which elevate the book.

The nameless and titular First Sister is a priestess-concubine on a starship run by the Earth-Mars Gaem theocracy. The Sisters hear confessions, relieve the tensions of the soldiers, and have their voices taken by surgery. When her captain departs, and doesn't take First Sister with him as planned, First Sister must embark on a desperate espionage mission while winning the favor of new captain, the wounded Hero of Ceres Saito Ren. She is allowed to write with Ren (an act normally forbidden to sisters) in order to reveal that the new captain is in fact a traitor. If she fails, she'll be unranked and given to the crew, or disavowed and executed by her own order.

Lito sol Lucius is the second viewpoint, a soldier with the Venus and Mercury based Icarii. The Icarii have had a longstanding lead in tech, based on hermium shields and drives using elements only obtainable on Mercury, but that lead has been eroded recently. Lito lost Ceres, and in losing it lost his partner Hiro val Akira. Lito and Hiro are linked via neural implants as paired duelists: rapier and dagger fighters who use shapeshifting mercurial blades. Lito is cooling his heels as a training officer when he gets a new partner and a new assignment. It seems Hiro survived the Fall of Ceres and has betrayed the Icarii. Lito's mission is to return to Ceres incognito, find Hiro, and assassinate them.

The third story is Hiro's, revealed in flashback as audio logs to Lito. Hiro is by any measure the proper protagonist of the book. Non-binary and the child of the terrifyingly powerful scientist and industrialist Souji val Akira, Hiro is looking to end the long and pointless war between the planets. He's also looking for justice for the Asters, a human subspecies modified for survival in deep space, and ruthlessly exploited by more baseline humans. And he wants revenge on his father for a childhood of lies and trauma.

The stories all build toward an explosive climax of revelations on Ceres, as our viewpoint characters decide where their true loyalties lie, and who they'll kill or save to enact their beliefs. There's a lot that I don't much care for in this book. The setting feels artificial and arbitrary, built of pieces lifted from other works rather than an organic whole, the pacing is a beat off, and Hiro is the real protagonist, with the other characters serving merely as lenses onto his plot. The silenced and submissive First Sister feels exploitative, though Lewis handles her with some delicacy. And as someone who reads a lot of these books, I can see these flaws, and I can also say they don't matter because of a sheer fearless verve in this book. I'm hoping Lewis will grow as an author, and look forward to book two.