on the book

English

(theater) Acting as a prompter.
- 1954, Harald Melvill, Theatrecraft: The A to Z of Show Business, page 103:
  That was the “set-up” in the Venner Repertory Company, and I must state that they needed very few prompts, even on the first nights of which we had two a week! I was “on the book” , gave all the “lighting and effects signals” […]
- 2004, Michael Hallifax, Let Me Set the Scene, page 340:
  I was on the book in the prompt corner on stage right.