This book aims to support its readers in an interactive way while working on the preludes and fugues from Bach's great two-volume piano work. Following a brief introduction to the nature, origin, and prerequisites of the "Well-Tempered Clavier," there is a compendium of all the questions one might ask in relation to a prelude or a fugue, as well as a detailed listing of additional information that serves as decision-making aids in answering these questions. In 48 individual chapters, each of the pairs of works is discussed in detail. Numerous musical examples, sketches, and graphical representations facilitate a creative understanding of the material, structure, and design possibilities of this foundational work of music literature.