The Millionaire Next Door by Thomas J. Stanley is a groundbreaking book that reveals the secrets of America's wealthy. Through interviews with hundreds of millionaires, Stanley reveals the common traits and strategies that millionaires use to become and stay wealthy. He also provides practical advice on how to build wealth
From Wikipedia
The Millionaire Next Door: The Surprising Secrets of America's Wealthy (ISBN 0-671-01520-6) is a 1996 book by Thomas J. Stanley and William D. Danko. The book is a compilation of research done by the two authors in the profiles of American millionaires.