For any serious investor, there is one weekend out of the year that you mark on your calendar. Around the last weekend in February or first weekend in March, on a Saturday morning, legendary investor Warren Buffett releases his annual letter to Berkshire Hathaway (NYSE:BRK.A) shareholders. For the past four decades, these letters have become gospel for not only value investors but for anyone serious about learning how to not only become a better investor, but also a better businessman, a better executive, and a more effective leader.

Buffett's letters, edited by his friend Carol Loomis, a long-time writer at Fortune magazine, are devoid of glossy charts and graphs, and most importantly, they are written in a very simplistic and relatable manner. As Buffett has said numerous times, he assumes the audience consists of distant relatives who only pay attention to Berkshire once a year and know nothing about its business happenings during that time.

Key Lessons from Buffett's Letters

Buffett's letters are an encyclopedia of investment and business education. But as Berkshire has morphed from a small textile operation to a conglomerate that sells insurance, hamburgers (Dairy Queen), paint (Benjamin Moore), and lollipops (See's Candies), Buffett's letters have become more of an educational read than simply a letter about the operations. The past five annual letters contain some very important themes:  

Equity Is Business Ownership, Not Stock Ownership

Perhaps the most important recurring theme in Buffett's letters has been the philosophy that when you invest in stocks, you are acquiring a partial ownership interest in a business, not just a ticker symbol. It's that view that, according to Buffett, separates the speculator from the investor. Buffett often likes to say that he is a better investor because he is a businessman and a better businessman because he is an investor.

Assume you own your own business and one day a buyer comes to you with an offer to buy your business at 25% below the value you feel your business is worth. Most likely, you would send that buyer away. Ironically, in the stock market, many people behave differently. They invest in a quality business and lo and behold, the market turns volatile and the stock price drops by 5%, 10%, or more. Nervous about the decline, many choose to sell. Yet, absent the discovery of fraud, what can really happen to a business overnight to make it worth 20% less than the day before? Nothing happens to the business; it's irrational human behavior. When you invest in businesses and not stock symbols, you are going to ignore this irrational noise.

Better Days Are Ahead For America

It's been over five years now since the Great Recession hit the United States. During the past five years, Buffett has specifically commented and discussed his bullishness on America. Buffett's defends his claim with a simple point: During America's 238-year history, when has it ever paid off to bet against America over the long run? Per capita income continues to grow, America's free market system remains the absolute best mechanism for growth and prosperity, and the U.S. remains the most innovative company on Earth, having spawned Google (Nasdaq:GOOG) and Apple (Nasdaq:AAPL), along with globally recognized brands, such as Coca-Cola (NYSE:KO), Nike (NYSE:NKE), and McDonald's (NYSE:MCD).

The Great Recession is a perfect example, Buffett suggests, as to why it pays to go long America. Five years later, the economy is clearly on the mend and the stock market has recovered all of its losses and then some. Japan, by contrast, has endured two decades of deflation and stagnation and its equity market remains a fraction of its all-time high set over 20 years ago.

Berkshire Hathaway Is in Good Hands after Buffett

Very few companies are branded by their CEO as Berkshire Hathaway is with Warren Buffett. The list of companies that were built like Berkshire is small: Standard Oil had John Rockefeller, Carnegie Steel had Andrew Carnegie, John Pierpont Morgan was J.P. Morgan Chase (NYSE:JPM), and Steve Jobs of Apple are among the few that come to mind.

Buffett is well aware of his effect on Berkshire and for years has taken time to discuss succession at Berkshire. Unlike many companies with legendary CEO's that lose luster once the chief is going, Buffett is ensuring that Berkshire Hathaway maintains its unique culture and its status as a fortress of safety. Once Buffett is gone, his job will be split into two - investment management and operations. Berkshire has hired two investment managers - Todd Combs and Ted Weschler - who are each investing $7 billion on behalf of Berkshire. The CEO-whose name is undisclosed-THAT RIGHT?-tapped to succeed Buffett has already been identified. Because Berkshire has many shareholders who view Berkshire as their retirement security, Buffett, in typical fashion, has taken time to update shareholders on the matter.

The Bottom Line

While Berkshire shareholders have been treated to an unbelievable wealth-creating machine over the past 50 years, Buffett has also given students, investors, and anyone else interested in investing an amazing gift in his annual letters. If you have any serious interest in investing, business, and good corporate governance, Buffett's letters are a must read.

Disclosure – As of this writing, the author is long shares of BRK.B.