These are books that have been discussed and recommended in the Bible Studies Live-Streams: 

Spiritual Counsels by Saint Paisios of Mount Athos - Volumes I-V

Reflections on Children in the Orthodox Church Today by Sister Magdalen

Conversations with Children, Communicating Our Faith by Sister Magdalen

The Way of a Pilgrim by R.M. French

Orthodox Saints by George Poulos

The Wisdom of the Greek Fathers by Andrew Louth

The Way of a Pilgrim by Gleb Pokrovsky

Ascending the Heights by Father John Mack

Thirty Steps to Heaven by Vassilios Papavassiliou