It is important to realize that this book was the first book Ken published on ACIM, in the period when he was still practicing psychotherapy and he had a number of Catholic clergy among his patients. He himself had let go of his inspiration to follow Thomas Merton into the abbey of Gethsemane, and instead devoting his life to working with A Course in Miracles. Within his collaboration with Helen Shucman as the scribe of the Course it was very clear that Helen had no interest in teaching the Course. That was to become Ken's domain and he sensed the calling early on.
As with anything, you can read this book on multiple levels, but one way of saying it is that it clearly reflects the time in Ken's life when he had just transitioned from his monastic aspirations to embracing the Course as his path. You could read the book as a commentary on the Christian ideals and the monastic tradition, and as such it is grounded in what is familiar from the Christian tradition, clarified and explained with the insights from A Course in Miracles, and in a way it is evident that to write about anything this well, you have already said goodbye - you have moved on.
In the context of Ken's teaching of A Course in Miracles, the important aspect here is that this book leverages to the hilt the Course's appeal to familiar terminology from the Christian tradition only to clarify, at times "correct" it, and explain it. The corrections are most often in the form of I said so and so, but it was misunderstood, and here is what I meant. Again the operative step in the process is that the Course firmly stands in Judaeo-Christian Culture and most specifically within New Testament tradition, and explains its true meaning better than anything could.
We know that Ken's doctoral thesis was about St. Theresa of Avila and it is an important step towards understanding the validity of the spiritual path as a psychological development towards becoming more integrated and whole. With shedding our attachment to the ego and the world, we are, however, not necessarily helped by seeking out a mountain top or a monastery - that amounts to putting form before content. That is the key insight from the Course. The spiritual path is our journey home, as portayed powerfully in the Odyssee, with all the temptations along the way, the only guide is our true self, expressed in the New Testament and A Course in Miracles in the figure of Jesus. The Christian tradition kept the figure of Jesus alive in the imagination, in spite of all the distortions and some quite gruesome episodes (think crusades, etc.). The appearance of A Course in Miracles radically returns us to the content over the form, for the Course is all about the inner process, never about the form.
This book explains that initial appeal of the Course to the familiar for those who came from a Christian tradition, and in practice it can help to deepen the inner dimensions of their faith. If your background involves any amount of Christian teaching, or even just Biblical studies, but you want to look deeper, this book could be helpful. For many already familiar with the Course and with some modicum of Christian education, it could be helpful to look at the deeper meanings that you likely had not fathomed before.