The book describes many New Thought beliefs such as the law of attraction,[2] creative visualization and man's unity with God, and teaches the importance of truth, harmonious thinking and the ability to concentrate.

At the beginning of the book is a Psychological Chart which readers are encouraged to complete, providing a self-evaluation of their creative power, time efficiency, health, mental ability and capacity to concentrate.

The sequence of exercises in each chapter is as follows: The ideas behind the book mainly come from New Thought philosophy, but there are influences from other sources such as Hinduism, Masonism and Rosicrucian teachings, Theosophy, and the Bible.

[8][9][10][11][12][13] It is claimed on the website haanel.com that Charles Haanel received a letter in 1919 from Napoleon Hill, who later went on to write one of the best-selling books of all time, Think and Grow Rich, saying that his own success was due to the principles laid down in The Master Key System.

Master Key System and Mental Chemistry, being published prior to 1923, are considered to be in public domain,[28] but several of his other books, being currently in distribution, are still covered by copyright law timeframe.