IF you have an interest in the underpinnings of the Eastern approach to Jesus Christ and the Trinity and the Church etc, then you would do well to read "The Orthodox Way" by Kallistos Ware, or, if you want to dig into some deeper theology, "The Mystical Theology of the Eastern Church" by Vladimir Lossky is a classic, as is the difficult but rewarding masterpiece "Being As Communion" by Zizioulas. ENJOY!
It is the second half of the book that really gets into an examination of the mystical tradition within the Eastern Orthodox Church. He views organizations such as EREVNA as representing the equivalent of the Hindu tradition of jnana yoga (the wisdom path to Spirit) while Orthodox Spirituality is more analogous to bhaki yoga (the devotional or ecstatic path.) To Erevra's credit its members hold that any mystical practice that leads to Christ consciousness is authentic religion, whether it be Mahayana Buddhism, Sufism, Vedanta, or Christianity. The Orthodox view is not always so charitable. In fact, much of mainstream Orthodoxy seems to be unfamiliar with its own roots having adopted the arid, rationalistic theology of Western pattern in an attempt to "modernize." In any case, the author actually travels to Mount Athos (Agion Oros) to meet and talk with more traditional practioners. He also discovers and briefly discusses the classical spiritual writings known as the Philokalia.
The closing section "Lifting the Veil" is especially good. It deals with the breakthrough of human consciousness in our times, and how we are finally evolving to a point where a significant number of individuals are learning to see beyond the primitive superstition of materialism. He points out that Kenneth Ring calls this the "shamanisation" of society.
This is third time that I've found myself reading this book. If you are primarily interested in the core of the perennial philosophy or tradition I also personally recommend The Only Tradition by Quinn, or Survey of Metaphysics and Esoterism by Schuon.