This is an audiobook summary of The Intelligent Investor.
The Intelligent Investor is based on value investing, an investment approach Graham began teaching at Columbia Business School in 1928 and subsequently refined with David Dodd. This sentiment was echoed by other Graham disciples such as Irving Kahn and Walter Schloss. Warren Buffett read the book at age 20 and began using the value investing taught by Graham to build his own investment portfolio.
The Intelligent Investor also marks a significant deviation to stock selection from Graham's earlier works, such as Security Analysis. He explained the change as:
The thing that I have been emphasizing in my own work for the last few years has been the group approach. To try to buy groups of stocks that meet some simple criterion for being undervalued -- regardless of the industry and with very little attention to the individual company... I found the results were very good for 50 years. They certainly did twice as well as the Dow Jones. And so my enthusiasm has been transferred from the selective to the group approach.