Bisection

Tria and Resa have shared the same body since they were born. Like everyone on their home planet of Kinaru, their mind and body are divided down the middle: the logical right and the emotional left. Tria, the right, has a budding career as a biologist, while Resa dreams of more freedom than their home planet grants her. When aliens land on Kinaru, Tria and Resa seize the opportunity to be the first of their people to travel to the stars.
Karnath, the alien scientist assigned to study them, is convinced there is more to the Kinaru than meets the eye. But only days into the trip, crew members start turning up dead, and the only answers may lie on a forbidden, war-torn planet-Earth. To solve a conspiracy that threatens three planets, Tria must find out the truth of who her people really are, and Resa needs to finally tell Tria the dark secrets she's been hiding all their lives.