hardcover vs playbook

hardcover

noun
  • A book with a rigid binding, often of cardboard or leather. 

adj
  • Having a rigid binding. 

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). 

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