The book opens a previously closed chapter for understanding Johann Sebastian Bach's last major instrumental cycle. The 'Art of Fugue' is not an autonomous musical work. It contains a non-musical aspect directed towards Christian beliefs. After deciphering the four initial notes of the main theme as a synonym for the biblical King David, the first half of the work is shown to be associated with the Old Testament, while the second half is linked to the New Testament. Wolfgang Wiemer's discovery aims to contribute to understanding, performing, and listening to the extremely strict yet highly expressive 'Art of Fugue' in homes, churches, and concert halls in a way that Bach envisioned at the time.