This book announces itself as the work of Three Initiates and presents its seven principles as a distillation of teaching descended from ancient Egypt through a line of Hermetic adepts. It is, on the evidence, a 1908 American book by a single identifiable author.
William Walker Atkinson was a former lawyer who became one of the most prolific figures of the New Thought movement, editing its magazines and publishing under his own name and under at least three pseudonyms, among them Yogi Ramacharaka and Theron Q. Dumont. Philip Deslippe's edition assembles the case. The book was issued by the Yogi Publication Society, Atkinson's own Chicago imprint. Its vocabulary, its habits of construction, its characteristic use of capitalised abstractions, and its underlying mental-causation doctrine all correspond to his signed work of the same years. The advertising in the back of contemporary printings is for his other titles.
The content is New Thought. The principle of Mentalism, that the universe is mental in nature; the principle of Correspondence, in the form "as above, so below"; the principle of Vibration, expressed in terms borrowed loosely from nineteenth-century physics, these belong to the American metaphysical religion of the turn of the twentieth century, and they read as such. They do not correspond closely to the actual Hermetic treatises, which are available and can be compared. The seven principles are not found there, and the Emerald Tablet, the one place the correspondence axiom does appear, is a medieval Arabic text rather than an ancient Egyptian one.
None of this makes the book worthless, and its influence is beyond dispute; a great deal of twentieth-century popular occultism, and a good deal of subsequent self-help, comes through it. But it should be shelved as what it is. It is a modern work of American metaphysical religion that adopted an ancient frame, and it is regularly cited as a primary source for Hermetic doctrine by readers who have not gone to the primary sources.
The pattern is the same as the one visible in the Golden Dawn's charter and in eighteenth-century Templar Masonry: a genuine composition presented as a transmission. It recurs often enough in this subject to be worth naming as a convention rather than treating each instance as a scandal.