Christian Astrology, written in 1647 by the English astrologer William Lilly, is considered to be one of the most important seminal works of Western astrology. William Lilly successively treats the rules of western astrology, horary astrology and 'nativities', about erecting and analysing a birth chart in natal astrology. He wrote the book when he was ill and had to stay at home. Running away from the plague in London, he spent a year in the countryside to study, reflect, and write Christian Astrology. Lilly himself explains that he was influenced among others by Ptolemy's Quadripartitum (Tetrabiblos), De occulta philosophia by Agrippa, De Astronima Tractarus 10 by Guido Bonatti, 120 Aphorismi of John Dee, Medicina Catholica by Robert Fludd, Epitomes Astronomiae by Johan Kepler and Paracelsus' De Meteoris, all of which are mentioned in the appendix of Christian Astrology. The modern edition of Christian Astrology consists of three volumes: Book 1: An Introduction to Astrology Book 2: The Resolution of all manners of Questions and Demands Book 3: An Easie and Plaine Method How to Judge Upon Nativities Source: Wikipedia (en)