paperback vs user guide

paperback

noun
  • A book with flexible binding. 

adj
  • Having flexible binding. 

verb
  • To issue or publish (a book) in a paperback edition. 

user guide

noun
  • A manual intended to assist in the use of a particular system. 

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