For a competent or semi competent guitarist (depending on your modesty!) who is aspiring to move into the area of songwriting, this book is a revelation. For so long we are used to seeing chord boxes and playing shapes and experiencing the sounds they make. After delving into this book for a while it becomes clear where the chords fit into musical theory and how it is possible to create a personal sound in a major or minor key with blues chords thrown in for good measure. It also helps when learning other people's songs because once you realize, for example, that a song moves from the 1 chord to the 5 chord as a first change, then you have another way of remembering a song.