A strange and anonymous pamphlet was published in 1740 and the ensuing quest to determine its authorship has, several centuries later, given rise to an intriguing and fascinating series of events. This has unfolded through detailed and meticulous bibliophilic analyses and have generated heated and controversial debate about the identity of the author of the pamphlet. The protagonists in this intellectual adventure are two celebrated economists - John Maynard Keynes and Piero Sraffa - who both lived and taught in Cambridge and were united by a close intellectual relationship as well as a profound friendship. And, naturally, a further major protagonist is David Hume himself, who is discovered to have been the nameless author of the pamphlet. The reconstruction of this intriguing episode, put forward in this compact and highly readable book, offers the opportunity to revisit the original Introduction on which the two Cambridge economists placed their joint signatures. It was published by Cambridge University Press in 1938, in an edition that also featured the facsimile text of Hume's short essay, which had lain in obscurity for almost two hundred years. Today, the pamphlet is reproduced in The Enigma of the Treatise. Key features include: (1) Economics is often regarded as technical, dry and not easy to read; however, this book, as its title The Enigma of the Treatise suggests, is far from dry and difficult to read. It follows the intricate trail of investigation into the mystery of who wrote the Treatise when and why. (2) The book is of interest not only to economists but also to historians and, in general, to bibliophiles for whom the controversial history of a given publication is, in itself, a subject worthy of investigation. (3) Although the philosophy of Hume is well known, the text discussed in this book is relatively poorly known, having lain in oblivion for several centuries until its revival by the two famous economists mentioned in the book (Keynes and Sraffa). (4) The examination of the two economists' contribution to the debate on the Abstract provides a hitherto neglected insight into their cultural and bibliophilic interests. (5) In contrast to many lengthy tomes on economics, which at times sacrifice the pleasure of reading to academic seriousness, The Enigma of the Treatise, of relatively short, ensures 'readability' that stimulates the interest of students; the book also reaches out (without sacrificing scholarly investigation) to the broader reading public of non-practitioners.