Question: A Treatise on White Magic is a book by Alice Bailey, a writer of how many books on theosophical subjects?
Context: The Great White Brotherhood, in belief systems akin to Theosophical and New Age, are said to be supernatural beings of great power who spread spiritual teachings through selected humans.  The members of the Brotherhood may be known as the Masters of the Ancient Wisdom or the Ascended Masters.  The first person to talk about them was Helena Petrovna Blavatsky (Theosophy), and after she and other people claimed to have received messages from them.  These included Aleister Crowley, Alice A. Bailey, Guy Ballard, Geraldine Innocente (The Bridge to Freedom), Elizabeth Clare Prophet and Benjamin Creme.  Machaelle Small Wright has written extensively about the "White Brotherhood" and her communication and work with them. Curuppumullage Jinarajadasa (16 December 1875, Sri Lanka–18 June 1953, United States) was an author, occultist, freemason and theosophist.  The fourth president of the Theosophical Society, Jinarajadasa was one of the world's foremost Theosophical authors, having published more than 50 books and more than 1600 articles in periodicals during his life.  His interests and writings included religion, philosophy, literature, art, science and occult chemistry.  He was also a rare linguist, who had the ability to work in many European languages. White Magic is a psychedelic folk rock group formed in Brooklyn, New York City, and led by singer/guitarist/pianist/composer Mira Billotte.  Billotte performs under this moniker both with accompaniment or solo, using a daf, shruti box, and singing a cappella.  She is a modern trobairitz and, invoking both traditional and experimental folk, White Magic's sound ranges from loud psychedelia to meditative trance. Djwal Khul (variously spelled 'Djwhal Khul', 'Djwal Kul', the 'Master D.K.', 'D. K.', or simply 'DK'), is believed by some Theosophists and others to be a Tibetan disciple in the tradition of ancient esoteric spirituality known as The Ageless Wisdom tradition.  The texts describe him as a member of the 'Spiritual Hierarchy', or 'Brotherhood', of Mahatmas, one of the Masters of the Ancient Wisdom, defined as the spiritual guides of mankind and teachers ancient cosmological, metaphysical, and esoteric principles that form the origin of all the world's great philosophies, mythologies and spiritual traditions.  According to Theosophical writings, Djwal Khul is said to work on furthering the spiritual evolution of our planet through the teachings offered in the 24 books by Alice Bailey of Esoteric Teachings published by The Lucis Trust; he is said to have telepathically transmitted the teachings to Bailey and is thus regarded by her followers as the communications director of the Masters of the Ancient Wisdom. A Treatise on White Magic is a book by Alice Bailey.  It is considered to be among the most important by students of her writings, as it is less abstract than most, and deals with many important subjects of her works in an introductory, even programmatic fashion.  It was first published in 1934 with the subtitle 'The Way of the Disciple'.  She promulgated White Magic as a discipline to serve humanity. White magic has traditionally referred to the use of supernatural or powers or magic for selfless purposes.  With respect to the philosophy of left-hand path and right-hand path, white magic is the benevolent counterpart of malicious black magic.  Because of its ties to traditional pagan nature worship, white magic is often also referred to as "natural magic". The Lucis Trust is a nonprofit service organization incorporated in the United States in 1922 by Alice Bailey and her husband Foster Bailey, to act as a fiduciary trust for the publishing of twenty-four books of esoteric philosophy published under Alice Bailey's name, and to fund and administer activities concerned with the establishment of "right human relations".  These include the Arcane School, a school for esoteric training, World Goodwill, Triangles, a lending library, "The Beacon" magazine, as well as the publishing company. Black magic or dark magic has traditionally referred to the use of supernatural powers or magic for evil and selfish purposes.  With respect to the left-hand path and right-hand path dichotomy, black magic is the malicious, left-hand counterpart of benevolent white magic.  In modern times, some find that the definition of "black magic" has been convoluted by people who define magic or ritualistic practices that they disapprove of as "black magic". Alice Ann Bailey (June 16, 1880 – December 15, 1949) was a writer of more than twenty-four books on theosophical subjects, and was one of the first writers to use the term New Age.  Bailey was born as Alice LaTrobe Bateman, in Manchester, England.  She moved to the United States in 1907, where she spent most of her life as a writer and teacher. Esoteric Buddhism is a book originally published in 1883 in London; it was compiled by a member of the Theosophical Society A. P. Sinnett.  It was one of the first books written for the purpose explain of the Theosophy for the wide range of readers, and was "made up of the author's correspondence with an Indian mystic."  This is the most significant theosophical work of the author.  According to Goodrick-Clarke, it "disseminated the basic teachings of Theosophy in its new Asian cast."
Answer: more than twenty-four