Thomson ReutersWarren Buffett, widely considered one of the world's best investors, is likely to tout the merits of passive investing this weekend to readers of his annual letter to Berkshire Hathaway Inc. shareholders. The letter, slated for release around 8 a.m. EST on Saturday, will probably focus on familiar themes for the 86-year-old Buffett, with many single-spaced pages reviewing Berkshire's businesses and managers, Wall Street, the economy and perhaps even politics. "The letters are written as much for sophisticated financial people as for people in high school," said Andy Kilpatrick, author of "Of Permanent Value: The Story of Warren Buffett." "It's a fun read, and when you get through it, you think, 'Wow, I could be doing better with my life and my investing.'" Buffett believes most stock investors are better off with low-cost index funds than paying higher fees to managers who often underperform.