Alfred Dürr, arguably the most famous Bach researcher of recent decades, presents here the culmination of his work on one of the central works in music history. In an accessible form and language, he introduces the universe of the Well-Tempered Clavier. In the introduction, he describes how the two volumes of the Well-Tempered Clavier were created, which types of preludes and fugues are included, what the well-tempered tuning is all about, and which performance practices should be considered today. In the main part of the book, structured like a reference work, each of the 96 pieces is discussed in detail. The origins, often in various versions, are gently explained even to the philologically inexperienced layperson. Performance-related questions are addressed, and styles, types, and models are described.