The Master Key System was originally published as a 24 week correspondence course in 1912. It was later published as a book form in 1916.The Master Key System is, without doubt, one of the greatest books ever written on the attainment of self-awareness and success.The twenty-four parts of this manual have been described as 'absolutely life-changing'. It was one of the two principle books which inspired the movie and best-selling book, The Secret.By 1933 it had reportedly sold over 200,000 copies worldwide. Haanel, the author, practiced the principles he taught in The Master Key System and became a self-made success who owned several major companies.Charles Francis Haanel (May 22, 1866 – November 27, 1949) is best known for his book The Master Key System which was published in 1912, when he was 46 years old. In addition to the Master Key System, Haanel wrote other books including Mental Chemistry, which was published in 1922.