The Orthodox Church by Timothy (now Bishop Kallistos) Ware is probably one of the best introductions to the Orthdox faith available in book form. It is helpful whether you are an Orthodox Christian looking to learn more about your own faith (me), a new convert, or someone who doesn't know anything about Orthodoxy at all. I have two major reservations which are really two parts of a larger problem, but besides these two issues I would recommend this book to anyone.
The first major problem is his unquestioning acceptance of the evolutionary theory. I can't say how many Orthodox do this but there is at the very least a highly vocal minority in favor of creationism (although this differs in some respects from the Protestant/Catholic model) and he does not address this at all. I personally would argue that the writings of the Fathers absolutely support creationism and that
we should not change their words to fit the western scientific world-view.
The second major problem is his easy approach to ecumenism and reconciliation with other Christian churches. I don't think we should alienate each other and we should, in my opinion, have some form of dialogue. However, he generally goes much further towards a sort of pluralism in denominations than I am comfortable with.
Still, his view of Orthodoxy theology is very sound and his explanations, geared as they are towards non-Orthodox, make this book accessible and very informative. In many cases topics I already knew something about were explained and clarified in a simple and understandable manner. I highly reccommend this book to anyone who wishes to learn more about Orthodoxy.