playbook vs reference book

playbook

noun
  • A book containing the text of a play or plays. 

  • A set of commonly employed tactics and strategies. 

  • A book of games and amusements for children. 

  • A book of strategies (plays) for use in American football (and by extension other sports or disciplines). 

reference book

noun
  • A book providing factual information. 

  • A book that can be consulted in the library but cannot be borrowed. 

How often have the words playbook and reference book occurred in a corpus of books? (source: Google Ngram Viewer )