Shardza Tashi Gyeltsen (1859-1934) is one of the most important luminaries of the Bon tradition of Tibet and certainly the most striking recent master of the teachings of the Great Perfection. Throughout his life, he applied the principles of the Great Perfection in numerous isolated retreats and perfected both spiritual realization and scholarly erudition. His works have nowadays become immensely important references for the modern Bon tradition, even if, for some lineage holders of this Tibetan school, he is best associated with the movement known as "New Bon". This widely diffused view, however, is wrong as is clearly shown by the analysis of Shardza Rinpoche's Collected Works in the present volume.