Gaining a deep understanding of the "soul" is a subtle process requiring both knowledge and practice, in addition to "time and circumstance," through which one absorbs the teaching and the experience(s) toward which those teachings are directed. Many writers have impressive insight into such knowledge (e.g., Wilber), and some have participated in aspects of the practice (e.g., Grof), but no contemporary writer has been able to fuse knowledge, practice, and interior experience into a corpus of work having such a unique clarity, depth, and eloquence appropriate to the contemporary Western audience as has Hameed Ali (literary name, A. H. Almaas). The reason for this is that no contemporary writer (with the exception of Idries Shah) has authoritatively addressed the nature and function of the subtle centers of the "lataif" or essential qualities (different from the "chakras"), and only Hameed's practice directly addresses the "activation of the lataif," which are the substance and expression of the mysterious "pearl" of the Soul. This knowledge and practice goes far beyond the rational and intellectual (e.g., 'philosophical') perspectives which can 'point to' these truths and cross-correlate them across world traditions but do not facilitate one's experiencing or 'tasting' them.
Discussion of such experience(s) requires a degree of "circular philosophizing" that is designed to show the reader how this knowledge resonates with what is in their cultural experience, such as orthodox psychology, German Existentialism, Sufism, Eastern religions, etc. (his Diamond Mind series), or how the practice resonates within the egos, minds, and souls of those who are attempting to "taste" their essential nature (his Diamond Heart series), and offers suggestions for how to pursue that practice (his Diamond Body series). Yes, one does indeed need a "frame of reference -- which is provided by Ali's other books," as is true with any authentic operative philosophy (Gnosis) designed to assist sentient beings (ordinary people) to begin to engage the full depth and essential nature of the Soul and situate that process within a larger Essential Reality that is indeed tangible and accessible to the soul. Hameed's work is not just another intellectual "philosophy" (and certainly doesn't deserve to be referred to as "semantic mush"), rather it is the current flowering of previously secluded Naqshbandi Sufi knowledge and practice related to the "activation of the lataif," arising out of 21st century Western soil carefully prepared by the decades of work by Idries Shah and others; this combined with the mature expression of the enneagram school of psychology and psycho-dynamic practice expressed in the lineage of Oscar Ichazo -- Claudio Naranjo -- Hameed Ali, another occasion where 1000 year-old esoteric Eastern knowledge and practice has emerged within the contemporary Western stream of cultural confluence.
I can concur (word-for-word, including the "30+ years") from personal experience with the previous reviewer¡s observation that participants with whom I have partaken of Hameed's Ridhwan school are "simply the most mature, developed, clean, clear, and simply HUMAN human beings I have ever known in the 30+ years I have been seeking out transcendental experience/ knowledge." For the most part they are serious and dedicated individuals who have been disillusioned, misled, or even "burned" by other paths or approaches and find the Diamond Work provides the substantive teaching and practice they have been seeking and previously not finding. Or they are simply people who have little experience of such "paths or approaches" but have been drawn, in one way or another, to this work, which they find necessary and appropriate for their personal development.
I have great respect for the work of Ken Wilber (have most of his books and have read half of them), and for the work of Stan Grof (have most of his works and have read or re-read most of them), and I would include the lesser known but equally sweeping, prodigious, and perhaps more comprehensive corpus of some 20 works by John G. Bennett, particularly his monumental 4-volume "integral" synthesis, _The Dynamic Universe_, but Hameed's work is of a different order, being the expression of a comprehensive philosophy, psychology, and teaching, honed over years of instrumental practice. In conclusion, I own more than 2000 volumes of "books," mostly on historical, cultural, scientific, philosophical, transpersonal, and transcendental topics, and, to put it simply, Hameed's books are on the "top shelf." I would encourage those seriously interested in self-knowledge and individual development to take the time to immerse themselves in Hameed's work and absorb its Essence.