I was reading a book on a long train journey from Paris to Nice by train that I read usually once a year. My girlfriend couldn't understand why I was reading a kids book as it had an elephant on the front. I told her it wasn't, but was in fact one of the most profound books about teaching you to think in a new way.

So I let her read it and she got about half way through and she totally got it and loved it. No harder than doing a crossword or a sudoku for the first time.

The book is: http://mitpress.mit.edu/books/little-schemer