This 61 p. essay has no Table of Contents, so, I provide it here:
Preface=p. 1;
I. A Warning to Esoterists=p. 3
II. The Coming of the Mystery Schools=p. 15
III. The Mystery Schools=p. 34.
Overall, it's a very basic text, decrying modern materialism, providing a "history" (or hagiography if you prefer) of the Mystery Schools, & a description of their acolyte preparations for guidance by a Master. It has a Theosophical &/or Alice Bailey (~7-rays) feel to it, though it mentions the Rosicrucians a few times.
THE GOOD--it provides moralistic guidance to seekers--not unlike the many religious ones such as the Four Noble Truths of Buddhism, but with less detail. It briefly mentions the Rosicrucians who are, indeed, a mystery school, & the Rosicrucian novel Zanoni: A Rosicrucian Tale (excellent IMHO). It has a couple of good quotations: p. 6: "The true occultist wants nothing but wisdom" & p. 21: "The Ancient Wisdom is the invisible spiritual side of religion which quickens the body of religion" with which I agree.
THE BAD--this work is loaded with very basic/elementary/trite platitudes. It speaks of "the gods" without explaining what/who is meant (obviously not Goddesses in Every Woman: New Psychology of Women which speaks the psychology that Hall rails against--without rationale) & he ranks philosophy > science. But, science (by adding empiricism to rationalism) goes beyond the speculations of philosophy. While these differences may be semantic, it appears that both psychology & science would contradict much of Hall's myth-like system. He also severely criticizes the rigidity of religion but HIS rigidity matches theirs! Hall praises occultism, ignoring mysticism--a MUCH higher discipline.
THE UGLY--Hall is specifically oriented towards "secret" organizations, implies that students are the same (one size fits all), & promotes spiritual slavery to The Masters. It's unknown whether his masters are the same as those of Theosophists, Rosicrucians, etc., but his are described as the ultimate--ignoring the Rosicrucian "Master Within," Jung's Self, or Creativity: Flow and the Psychology of Discovery and Invention. Further he speaks little of the non-theistic Absolute (e.g. Hindu Brahman, Kabbalah Ein Sof, Buddhist Ground of Being or Mind Itself, etc.) which is obviously beyond individual masters.
CONCLUSIONS--while there are some good observations/recommendations in this small work, it's much too rigid for my taste, somewhat dated I believe, & quite elementary. There are MUCH better books available. I'd recommend: Unto Thee I Grant (Rosicrucian Library, Volume No. V), The Initiate, Wisdom of the Mystic Masters, Kybalion: A Study of the Hermetic Philosophy of Ancient Egypt and Greece, or the works of Raymond Bernard such as "Secret Houses of Rose-Croix" & "Messages from the Celestial Sanctum." These are all from the Western tradition. There are many Buddhist books of great value (e.g. Zen & Tibetan) including my personal favorite Dzogchen. A great start are the many works of the Dalai Lama such as An Open Heart: Practicing Compassion in Everyday Life, Dzogchen: The Heart Essence of the Great Perfection, & The Gelug/Kagyu Tradition of Mahamudra. These have a more positive orientation than does Hall's work.