Sefer ha-Zohar, "The Book of Radiance," has amazed and overwhelmed readers ever since it emerged mysteriously in medieval Spain toward the end of the thirteenth century. Written in a unique Aramaic, this masterpiece of Kabbalah exceeds the dimensions of a normal book; it is virtually a body of literature, comprising over twenty discrete sections. The bulk of the Zohar consists of a running commentary on the Torah, from Genesis through...