Vladimir Lossky 
Mystical Theology of the Eastern Church [PDF ebook] 

Lossky’s great work on Eastern Orthodoxy covers the whole range of its spirituality and theology. Combining careful theology with the warmth of the deep personal devotion of the author, ‘The Mystical Theology of the Eastern Church’ is the best introduction to Orthodox teaching and theology available. It provides a reliable and informative presentation of the theological spirit of the Eastern Church. His account makes clear the profound theological differences underlying the practices of the East and West, and yet it is also an important contribution to ecumenism and to the life of Christian devotion. It brings together subjects that are more usually separated, asserting that there is no true mysticism that is not firmly rooted in theology, and no true theology that is not experienced, and therefore mystical. The tradition of the Eastern Church is presented as a mystical theology with doctrine and experience mutually conditioning each other.