The Orthodox Church by Timothy Ware: This goes into a lot of the history of the OC, which is very important and helpful to know.
How Are We Saved? by Timothy (Kallistos) Ware: This book is easy to read and succinctly, clearly describes the OC views on justification, sanctification, sin, human sinfulness, and overall salvation. I'm about halfway through it now, so I can't give a fuller idea of the book at this time. The author makes sure to point out specifically how the OC differs from Roman Catholic, Lutheran and Calvinist theology in this area, though I suspect it doesn't exhaustively cover these differences.