Bread & Water, Wine & Oil--An Orthodox Christian Experience of God by Archimandrite Meletios Webber is an excellent introduction to Eastern Christian spirituality. Archimandrite Webber writes in a way that is inspiring, clear and respectful.
Part I: Life as Mystery lays the groundwork for understanding the Orthodox approach to God and our relationship to God. It does an excellent job of explaining the difference between the "mind" (feelings and logic) and the "heart" (where God dwells), who God is and how we can really know Him (as opposed to what we *think* we know about Him), as well as specifics of fasting, prayer and icons.
Part II gets into the Divine Mysteries (sacraments) themselves, examining the specifics of how they are done and why. It opens up new meaning to each, especially if you come from the western Christian tradition.
This is a book that will be read again and again, dog-eared and highlighted beyond recognition.