The most up-to-date account of the Scottish architect and designer Charles Rennie Mackintosh's masterwork The Mackintosh Building at The Glasgow School of Art is a monument of international significance in the history of architecture and design. Designed by Charles Rennie Mackintosh (1868–1928), its soaring studios and atmospheric spaces would serve to educate and inspire generations of architects, artists, and designers, as well as attract visitors from around the globe. This book presents the updated story of "The Mack," incorporating for the first time the history of the building during the post-Mackintosh era up to the present day, including the May 2014 fire, reconstruction efforts, and the devastating fire of 2018 that destroyed most of the building. Illustrated with historical and archival images, reconstruction photographs, and visualisations using the latest 3D scanning technologies, it presents a comprehensive history of the context and creation of this building. The book updates knowledge of the building gleaned from the reconstruction process, including corrections of well-rehearsed assumptions. It also addresses controversies surrounding the second fire, examining issues around fire management that have received much public scrutiny. Including new and unpublished images, The Mack explores the significance of Mackintosh's masterwork, its international design importance, and its profound impact on its community of users.