This book consists of a stream of letters from Swami Satyananda to a female disciple written around 1960. The book does not provide us with her perspective which however can be inferred from the tone of Swami's missives which is at times encouraging, admonishing, disappointed and congratulatory. The book lays out, in no uncertain terms, the requirements laid down generations ago (perhaps by the original Shankaracharya himself) that need to be met before Kundalini is to wake within a safe and non-selfish container. These demand absolute discipline, an ethical stance, commitment to others and rigorous daily physical, mental and spiritual practice.
It is all in here. The mantras, visualization practices, energy practices, crystal gazing, long-distance healing, thought transmission. It is a system and Bihar Yoga has it down. The tradition is very clear about what is required from the lay person, what is possible and what are the no-nos. Absolute obedience to the guru is a precondition. The system "cannot be given to the weak, to the one attracted by sex, to the credulous, to the undevoted or unsurrendered one, to the lustful one, to the non-yogi, to one who is a slave of the body, mind and material possessions; not to one who is not a sadhaka, nor to one who is not a Hindu - never indeed to him!" [p. 63]. I guess this shortens the pool of potential applicants :). Perhaps things have changed a bit since the 60ies.
Even non-Hindus, however, can now see the beauty, rigor, profoundness, clarity, impecabbility and commitment to the welfare of the planet by the system presented by Swami Satyananda. Reading about it I was inspired, amazed, and grateful that such teachings exist and are transmitted across the ages.