Even Buffett Isn't Perfect (2008) by Vahan Janjigian
Most books about Warren Buffett tend to focus on his long-term investing success and rarely offer much in the way of criticism. In contrast, the aim of this book was to discuss some of the inconsistencies and potentially problematic aspects of his approach to investing, with the goal of helping readers learn from Buffett's missteps. However, I was disappointed in how the author went about trying to achieve that goal.
A prime example is the first chapter, which discusses Buffett's views on diversification. The author argues that Buffett is inconsistent on the topic: Sometimes he has advocated that investors maintain a small portfolio of 5-10 stocks that they know really well, whereas there are other times he has advocated widespread diversification via passive investment in index funds. What the author does not seem to fully appreciate is that Buffett's views were addressed to different kinds of investors. If someone has the time, knowledge, and ability to thoroughly evaluate companies and actively manage a portfolio (which Buffett is capable of doing), then it makes sense to have a small portfolio that represents only the very best investment prospects. However, if an investor lacks those qualities and is not interested in active portfolio management, then it might make more sense to passively invest in index funds.
There are some other purported inconsistencies, such as whether Buffett invests more for value than for growth, and the extent to which he conducts due diligence when buying entire companies. The latter criticism is in reference to Buffett mentioning in letters that he has sometimes made acquisitions within a day or two of being contacted about the possibilities. In the last few chapters the author discusses Buffett in relation to corporate governance, stock options, and taxes, but these issues mainly serve as springboards for the author's personal opinions, which may or may not be any better than Buffett's. Overall, I did not come away with an improved understanding of Buffett's imperfections or how they might inform my investing strategy.
Note: I read this book in November 2012.