J.R.R. Tolkien's literary cosmos may not be the most elaborate of the imaginary worlds in existence, it is certainly the most influential. The posthumous editorial work of Tolkien's son Christopher has also shown that Arda remains unrivalled in its consistency and complexity. Additionally, the re-publication of Tolkien's Andrew Lang lecture 'On Fairy-stories' (originally delivered 1939) and its interpretation within the discourse of literary fantasy has further strengthened his position as one of the foremost proponents of literary world-building or, as he himself preferred to call it, (literary) subcreation.The contributions to this volume by Tom Shippey, John Garth, Mark J.P. Wolf, Kristine Larsen, Andrew Higgins, Allan Turner, Gergely Nagy, Renée Vink, and a dozen other scholars, discuss not only Tolkien's theoretical concepts as well as his literary work but also explore the relationship between Tolkien's approach with that of other 'literary world-builders' whose imaginary worlds have attracted readers and scholars alike.