My daily list includes: The Bible & Holy Fathers for Orthodox edited by Johanna Manley,
The Prologue of Ohrid (St. Nikolai Velmirovic), Thoughts for Each Day of the Year (St.Theophan the Recluse).
I haven't been Orthodox long enough to have read many books twice but "Unseen Warfare" is definitely on my read again list. When I first read it I felt I could just keep re-reading that one book and be rightly guided.
What about you? What are the core Orthodox books you really live with and would miss the most if they were taken from you? (let's assume the Bible is a given and need not be mentioned...)