The Book of Zohar is the most revered book in Kabbalah. "Kabbalah/ Kabala is a discipline and school of thought concerned with the mystical aspect of Rabbinic Judaism. Its full theosophical system emerged in 11th-13th century Southern France and Spain, later being recast in 16th century Ottoman Palestine, though incorporating earlier Chaldean science, and derivative Jewish mystical forms. In turn it became the central foundation of later Jewish mystical development. Kabbalah is a set of esoteric teachings meant to explain the relationship between an eternal and mysterious Creator and the mortal and finite universe," informs summary at Pirate Bay.
You may learn a little about the Zohar and Kabbalah in this History channel documentary.