Jim McManus, a Redemptorist, provides an excellent overview of Marian beliefs and devotions in the Christian tradition. Although there is a focus on Mary as she is represented in Roman Catholicism and Eastern Orthodoxy, the book also provides a good summary of Marian devotion in other denominations (Anglican, Methodist, Presbyterian). McManus offers, without forcing anything on the reader, a Scripturally-sound and very well-argued case for the role of Mary in the life of any Christian believer... for non-Christians desiring to know more about Mary in Christianity, and for Christians wondering about their fellow Christians' practises, this book is perfect.
Then he said to the disciple, 'Behold, your mother' (John 19:27)