explorer vs travel book

explorer

noun
  • A person who by means of travel (notably an expedition) searches out new information. 

  • One who explores something 

  • A visual representation of a file system etc. through which the user can navigate. 

  • Any of various hand tools, with sharp points, used in dentistry. 

travel book

noun
  • A book about travelling to a certain region, such as a memoir or guide book. 

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