Alice Bailey wrote this book under the tutelage of the Master Djwhal Khul (the Tibetan), a Master of the spiritual "Hierarchy", headed by the Christ. These books comprise genuine, albeit advanced teachings about the Ancient Wisdom (this book however was written by Alice Bailey herself, and is a good introduction/less complex).Spiritual advancement can be expedited by these teachings to those willing and able to learn and grow spiritually. Most of what we know and have been taught about spirituality, the after-life, God, angels, souls, and spiritual evolution is basically erroneous information (analagous to children realizing their is no santa claus or easter rabbit when the higher truth is revealed). This has been further distorted by misguided zealots of all faiths, who accept as dogma the distorted and biased teachings of man-made theologies, and not the one true universal Religion of the Ancient Wisdom (as revealed in the Bailey books). The spiritual truth and reality has been kept alive (besides the Ancient Wisdom) by the mystics and secret esoteric shools throughout the ages. However, even they only have portions of the whole spiritual truth. if you read the Alice Bailey books and are unable to comprehend them fully, another (intermediate) area of study is recommended- Rosicrucian/AMORC (800 88-AMORC).
Also recommend reading (besides all the Alice Bailey books)- Vera Stanley Alder; Zachary Lansdowne; Douglas Baker; Cecil A. Poole; Raymund Andrea; Henry Guy ("Saving the World"); Three Initiates ("KYBALION").