A courier who joined Discovery and became Burnham's partner.
Cleveland Booker, known as Book, is a courier introduced in the third season of Star Trek: Discovery, played by David Ajala. He makes a living hauling cargo across a galaxy still scarred by the Burn, travels with a large cat named Grudge, and is the first person Michael Burnham meets when she arrives in the thirty-second century.
Book is a Kwejian, and his people share an empathic connection with living things. That gift lets him interface with the mycelial network and navigate Discovery's spore drive when needed. He and Burnham become partners in work and then in love, and he joins the crew.
In the fourth season his homeworld Kwejian is destroyed by the gravitational anomaly that threatens the galaxy, killing his family, including his nephew Leto. Grief drives him to break with Burnham and the Federation to try to destroy the anomaly on his own, but he later seeks to atone, and the two reconcile in the final season.