Think and Grow Rich is a classic motivational book. Written by Napoleon Hill and inspired by Andrew Carnegie, it was published in 1937 at the end of the Great Depression. In his introduction, Hill refers to the "Carnegie Secret", a conception which he reports is the foundation of all success and appears to be the premise of the book. Hill promises to indirectly describe this "secret" in every chapter, but never state it plainly, believing the use of the secret is only available to those who possess a "readiness" for it, a disposition Hill describes as essential to the concept itself.
Napoleon Hill talks about "The Secret" to Think & Grow Rich - Napoleon Hill - YouTube