The two works translated in the book, Mumonkan (The Gateless Gate) and Hekiganroku (The Blue Cliff Records), both compiled during the Sung Dinasty in China, are the best known and most frequently studied koan collections, and are classics of Zen literature. In a completely new translation, together with original commentaries, Katsuki Sekida brings to these works the same fresh and pragmatic approach that made his Zen Training so successful.