textbook vs true to form

textbook

noun
  • A coursebook, a formal manual of instruction in a specific subject, especially one for use in schools or colleges. 

adj
  • Having the typical characteristics of some class of phenomenon, so that it might be included as an example in a textbook. 

  • Of or pertaining to textbooks or their style, especially in being dry and pedagogical; textbooky, textbooklike. 

true to form

adv
  • According to one's nature; as expected. 

How often have the words textbook and true to form occurred in a corpus of books? (source: Google Ngram Viewer )