"Music-making is one of the happiest ways of employing some spare time and is one of the few things that you can enjoy alone or with others. I have therefore chosen some songs that I have known since childhood, and others which I came to know and love at school. Some are in French and German, and as songs are universal they may open the door to friendship in a wonderful fashion when you are away from home. Playing the piano with another person is always good fun, so I have arranged some settings as piano duets."
source: the editor in the book's foreword