What Comes First? Book or Idea?

Moving on to another reimagined book project, the question comes to mind "What comes first, the book or the idea?  Does a person have an idea and locate the book with which to use, or is a book within a pile of old books become inspiration itself?  Does a title stand out or does the shape of the gourd lend itself to being reimagined with a book?  In this instance, a book and gourd come together at about the same time: The Minstral's Daughter and a gourd curiosity from the garden with a shape similar to a viola.

The gourd was grown between two boards and therefore has a flattened body.