Elements of Astrology (1898) p.7. Broughton describes its value to astrologers as "One of the best books the student should read, and which is most essential" p.v.
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Robbins (1940) 'Translator's Introduction' II, p.xii. Analogies between the status of the Tetrabiblos in astrology and the Bible in Christianity are frequent. See for example Riley (1974) p.235, "virtually the Bible of astrology"; Broughton, Elements of Astrology (1898) p.7: "Ptolemy’s Four Books on Astrology are to the European and American Student what the Bible is to the student of Christian Theology"; Tucker, Principles of Scientific Astrology (1938) p.32: "it is the Tetrabiblos which interests astrologers... it is their astrological bible"; and Zusne, Jones, Anomalistic psychology: a study of magical thinking (1989) p.201: "the astrologer's bible, the Tetrabiblos, is still in use in the Western world".