playbook vs softcover

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). 

softcover

noun
  • A book having such covers. 

adj
  • Having covers made of paper or thin cardboard; paperback. 

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