A newer release of the 1968 publication (see my more extensive comments under ASIN= 0877281033), it's a translation of 3 Zohar portions, commentary on the Book of Concealed Mystery, & notes on the Greater Holy Assembly & Lesser Holy Assembly. Mathers did Kabbalists a service rendering these into English almost a century ago, but the later Simon & Sperling version (2000 pages long, ASIN= 0900689390) is more complete. Mathers version occasionally reflects his Christian occultism, but mostly provides useful observations & cross-cultural parallels. While his comments are helpful, they only scratch the surface of the deep symbolism. He shows parallels with alchemy & (as Jung approached alchemy), meaning emerges with extensive reading/study. However, Mathers': archaic language, spelling (e.g. words with excess letters), incorrect use of I vs. Y, & retention of Latin passages (based on Knorr von Rosenrath's somewhat suspect, `Kabbala Denudata') make the work less accessible to modern readers. It also contains some errors & omissions (e.g. Gematria 18 = Hebrew "life").
The 3 parts translated here are perhaps the most occult in the Zohar, seemingly a commentary on the Shi'ur Komah literature's symbolically physical description of God. It's an extremely esoteric work. Some of its significant points are:
1) Male & Female are equal in Kabbalah. "Where there is unbalanced force, there is the origin of evil."
2) 4 completes 3 = Carl Jung's Quaternity = Mathers' quaternary--"The trinity is always completed by & finds its realization in the quaternary."
3) "For commencement denotes end, & end denotes commencement; how, then, in the Absolute can there be either? Nevertheless, in the Absolute must we seek for the hypothetical starting-point of life." This is quite similar to Tibetan Buddhist ideas of origination or (more accurately) lack thereof.