Book excerpt: He is considered the father of modern astrology: Alan Leo opened up the secrets of divination by the stars to the general public in the early 20th century with a popular line of astrology manuals that set off a craze for horoscopes that continues to this day. Here, in this replica of the 1910 fourth edition of his essential primer, Leo teaches us. . the basics of astronomy required for an understanding of astrology . the nature and character of the twelve signs of the Zodiac . complete breakdowns of the affect of the Sun and the Moon on each house . what a horoscope is and how to cast one . and more. ALSO FROM COSIMO: Leo's The Key to Your Own Nativity, Symbolism and Astrology: An Introduction to Esoteric Astrology, Horary Astrology, and Mars: The War Lord British astrologer WILLIAM FREDERICK ALLAN (1860-1917), aka Alan Leo, published Astrologer's Magazine as well as a line of astrological materials; he founded the Astrological Lodge of the Theosophical Society in 1915.