This book offers a critical update of current Wittgenstein research on the Tractatus logico-philosophicus (TLP) and its relation to the Vienna Circle. The contributions are written by renowned Wittgenstein scholars, on the occasion of the "Wittgenstein Years" 1921/1922 with a special focus on its origin, reception, and interpretation then and now. The main topic is the mutual relation between Wittgenstein and the Vienna Circle (esp. Schlick, Waismann, Carnap, Gödel), but also Russell and Ramsey. In addition, included in this volume are new studies on Wittgenstein's life and work, on the philosophy of the TLP, and on the Wittgenstein family in philosophical and historical context. Furthermore, unpublished documents on Wittgenstein and Waismann from the archives are provided in form of edited and commented primary sources. As per the book series' usual format, a general part of this Yearbook covers a study on Neurath's economy as well as reviews of related publications.