The Sefer Yetzirah is the fundamental source of the Kabbalah. Numerous editions of the text exist. Each describes the creation of the universe in different ways. The differences relate to the different Kabbalistic Schools that used the text. No edition contains the full knowledge of the different Schools; thus, it is necessary to study the different versions of the Sefer Yetzirah to gain a fuller understanding of the Kabbalah.--amazon.com.