The seventh volume of Cath Thompson's highly acclaimed series of books on the subject of English Qaballa is an in-depth study of the metaphysical philosophy of the system discovered by James Lees. Thompson follows a trail of numeric correspondences through more than forty years of magical research and endeavour, from the earliest examples of English gematria to the feminine principle at the core of English Qaballa.

She sets out the evidence of a matriarchal cosmology, presenting a fully functional complementary alternative to the patriarchy of western occult tradition, based on pre-existing symbolism reinterpreted through the EQ lens. Thompson describes the characteristics of the primary deities in the Book of the Law according to EQ and includes an analysis of the Great Goddess Babalon.

She shows how EQ makes connections between celestial phenomena and human life with corresponding numerical values of significant words in the canon of esoteric language, describing the logical mathematical proofs of the English Qaballistic view of reality. She also discusses the psychology of the individual and the problems associated with the fact of mortality from the perspective of a modern magician.

English Qaballa: The Mystery of the Letters includes an overview of the Ordeal X, the Complete Tree of Life, the Scarlet Woman, and provides three rituals which the practitioner can use to situate themselves in the EQ current. .