This opening chapter presents a short synopsis of the book, pointing out its main themes and theses. Above all, this is not an introductory book on Wittgenstein’s Tractatus and on his later writings. Its content can be summarized in terms of three key elements. Firstly, the book probes Wittgenstein’s thought at its most fundamental philosophical level and in that connection engages with different interpretations advanced in recent decades. For example, we note that the Tractatus discusses mysticism, but make clear that its “fundamental thought” and method have nothing to do with mysticism (§ 4.6). Secondly, the book defends the One-Wittgenstein interpretation. It demonstrates that the method Wittgenstein followed in his Tractatus and in Philosophical Investigations was substantially the same (ch. 11). A key task of our study is to outline and elucidate this reading of the two seminal works. Thirdly, we present Wittgenstein’s method as an epitome of the project of analytic philosophy (ch. 12): Wittgenstein adopted and deepened the method of Moore and Russell and fused it with that of Frege. Further, we explore the attempts to adopt Wittgenstein’s method and philosophy by the Vienna Circle, the Cambridge school of therapeutic analysis and the Oxford ordinary language philosophy. Finally, we assess the influence of Wittgenstein on major representatives of analytic philosophy and also the touching points of his philosophy with leading figures in the history of philosophy in general (§§ 5.2; 11.8).