The sacred volume of the people of Yonada, kept inside a monolith in the Oracle's chamber, which holds the truth about their world-ship and the instructions for reaching its control room.
The Book of the People appears in the third-season episode For the World Is Hollow and I Have Touched the Sky, set in 2268. Yonada is a hollow asteroid ship built ten thousand years ago by the Fabrini to carry survivors from their dying sun, though its inhabitants believe they live on a planet.
The book is kept in a compartment of the monolith in the Oracle's room, and tradition says it is to be opened only when the people reach their promised world. The high priestess Natira shows McCoy where it lies after he agrees to stay as her husband.
McCoy passes the information to Kirk and Spock. They take out the book, follow its diagram to the hidden control centre behind the altar, shut down the Oracle and correct the course that would have ended in a collision with Daran V. The Fabrini records also hold a cure for McCoy's xenopolycythemia.