Think an Grow Rich! (ISBN 1-59330-200-2) is a motivational book. Written by Napoleon Hill and inspired by a suggestion by Andrew Carnegie, it was published in 1937 at the end of the Great Depression. It was the biggest seller of Napoleon Hill's books, selling a claimed 20 million copies over the next 50 years (although Alice Payne Hackett's 70 Years of Best Sellers suggests the figure was considerably lower).