In his thorough analytical study of Beethoven's Piano Sonata in E, Op. 109, Nicholas Marston suggests a unique way of understanding this important work. The book provides an exhaustive study of its sources and an analytical approach to the structure of the sonata itself. The source study is based on a complete transcription of all the surviving manuscript sources for the work; the book includes a large majority of the sketches, and parts of the autograph score. The introductory chapter reviews Heinrich Schenker's work on Op. 109. In Chapter 2 Beethoven's letters, conversation books, sketchbooks and other sources are used to build up a detailed picture of the progress of his work on the sonata. The middle chapters form the core of the analytical study in which the sketches for each part of the three movements are analysed in detail, and the relevance of the sketches to the final version is explored. The final chapter extends the notion of "sketch" beyond Op. 109 and summarizes the results of the study.