A book that I'd recommend on the subject is Lossky's Mystical Theology of the Eastern Church.
It's an excellent book, but it isn't easy reading.
Ah, but you see, the challenge and reward is exactly what I love so much about Orthodoxy. All of these numerous concepts seem mind-numbingly complicated bizzare at first. But once you begin to get the hang of things, it's jaw-droppingly simple how they all fit into place. I would concur, though, that you should have a pretty good grasp on Orthodox theology before getting into the advanced stuff. OP, if you need any recommendations on that front, I'm very well-equiped (which books that I actually have read, heh).