First, I want to state my objection to another review concerning the status of the author. According to that review the book should be dismissed as fraud because it's author was not Dionysius the Areopagite but a man who lived several centuries after him.
The review goes on to add that had not the supposed author been Dionysius the work would not have fared the esteem it has. This opinion is wrong and misinformed. I explain (although I'm sure that almost anyone who gets into the trouble to seach for Dionysius, or better Pseudo-Dionysius has no need for this explanation): the practice of attributing a book to a person whose name would lend authority to it was very common in late antiquity. So to call it a fraud is anachronistic. It does not follow from the fact that we would regard such an act of misattribution now as a "fraud" that it was considered as such at a different age. Educated people in late antiquity knew that many works were misattributed and in many cases they also knew which.
Now as far as the value of the work itself is concerned: Filologists have shown that some of Plato's works could not have been written by him, there are also great disputes about who the persons who wrote the gospels were and so on. Yet the name of the author does alone does not make a great work. So from "Pseudo-Plato" we have "On Virtue". Who knows this work? And there are gospels attributed to Thomas and other pupils of Jesus that are not canonical. Yet the writtings of Pseudo-Dionysius have had a lasting influence in Christian thinking and this fact is owed solely to their merits.
In these works P-Dionysius propounds an original idea: God's essence apart from what is revealed in scripture is unknown, yet an intellectual Christian has every right to exercise his mental powers and philosophize on God.How can this be done? Dionysius answer is that this can be done through a negative way, through saying what God is not, to put matters crudely.
In particular this method is expounded in The Divine Names in three stages. In the first stage God is described tentatively as One, or Virtue and his essence is being comprehended through his emanating powers such as Wisdom, Life-in-itself, Being qua Being. This stage is followed by another were the world as revealed by the senses is seen by Dionysius as a symbol or analogy to God's essence. The first stage represents man's search of God through the intellect and shows the limitation of this search. The second stage sees the Kosmos as a visible symbol of God and represent man's comprehension of God through a symbolic comprehension of it. However, both stages reveal a limited comprehension of God: it's not through our intellectual powers that we can reach God, nor through the symbolic comprehension of the sensible world. So both these ways though helpful to our way to God must be annuled, or better be transcended in order to give place to a mystical union with Him in a loving ecstatic relationship.
This is undoubtedly one of the great works of Christian thinking in the same rank with Augustine's City of God. Yet although it preaches the limitation of any attempt at an intellectual comprehension of God, the book is a heady work of abstract Christian philosophizing. But this does not make it contradictory, actually it's a Critical work of Christian theology, in the sense Kant gave to the term: it shows the limits of the intellect to make space for a mystical, lived, union with God. The book is full of wondeful metaphors, symbolisms and you can rarely find such a wonderfully written work of abstract thinking. If you enjoy abstract thinking you will enjoy the book either you are a Christian or not (and this might be one of the drawbacks of the book considered from a Christian point of view).
This book completely transformed the way that I relate to God. Although the text can be a little rough until you ease into the mindset, it is well worth the discipline. Completely in line with Orthodox Christianity, yet delving into a much neglected area.