"on the book" meaning in English

{
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "prepositional phrase",
        "head": ""
      },
      "expansion": "on the book",
      "name": "head"
    },
    {
      "args": {},
      "expansion": "on the book",
      "name": "en-PP"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "prep_phrase",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Theater",
          "orig": "en:Theater",
          "parents": [
            "Art",
            "Entertainment",
            "Culture",
            "Society",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "1954, Harald Melvill, Theatrecraft: The A to Z of Show Business, page 103:",
          "text": "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” […]",
          "type": "quote"
        },
        {
          "ref": "2004, Michael Hallifax, Let Me Set the Scene, page 340:",
          "text": "I was on the book in the prompt corner on stage right.",
          "type": "quote"
        }
      ],
      "glosses": [
        "Acting as a prompter."
      ],
      "id": "en-on_the_book-en-prep_phrase-E7Bq16Az",
      "links": [
        [
          "theater",
          "theater"
        ],
        [
          "prompter",
          "prompter"
        ]
      ],
      "raw_glosses": [
        "(theater) Acting as a prompter."
      ],
      "related": [
        {
          "word": "hold the book"
        },
        {
          "word": "keep the book"
        },
        {
          "word": "on the books"
        }
      ],
      "topics": [
        "entertainment",
        "lifestyle",
        "theater"
      ]
    }
  ],
  "word": "on the book"
}

{
  "head_templates": [
    {
      "args": {
        "1": "en",
        "2": "prepositional phrase",
        "head": ""
      },
      "expansion": "on the book",
      "name": "head"
    },
    {
      "args": {},
      "expansion": "on the book",
      "name": "en-PP"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "prep_phrase",
  "related": [
    {
      "word": "hold the book"
    },
    {
      "word": "keep the book"
    },
    {
      "word": "on the books"
    }
  ],
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English prepositional phrases",
        "English terms with quotations",
        "Pages with 1 entry",
        "Pages with entries",
        "Quotation templates to be cleaned",
        "en:Theater"
      ],
      "examples": [
        {
          "ref": "1954, Harald Melvill, Theatrecraft: The A to Z of Show Business, page 103:",
          "text": "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” […]",
          "type": "quote"
        },
        {
          "ref": "2004, Michael Hallifax, Let Me Set the Scene, page 340:",
          "text": "I was on the book in the prompt corner on stage right.",
          "type": "quote"
        }
      ],
      "glosses": [
        "Acting as a prompter."
      ],
      "links": [
        [
          "theater",
          "theater"
        ],
        [
          "prompter",
          "prompter"
        ]
      ],
      "raw_glosses": [
        "(theater) Acting as a prompter."
      ],
      "topics": [
        "entertainment",
        "lifestyle",
        "theater"
      ]
    }
  ],
  "word": "on the book"
}