Books constitute capital. -- Thomas JeffersonThe only way to ensure a happy retirement is to become an investing autodidact. "Autodidact" is a good 50-cent word for a self-educated person, and it's basically what individual investors are forced to become these days. We are increasingly responsible for managing our own retirement plans and fund investments, yet most of us receive no formal education in prudent investing -- or even an informal education from our retirement-plan sponsors and advisers. How are investors expected to manage their financial destiny when they are woefully uninformed? Go out and buy a few good how-to books. A few well-chosen investing books -- provided you read them, of course -- may turn out to be the best investments you ever make. I get asked this question quite often: What are the best investing books to buy? The books listed in today's column are the ones I suggest most often. Some make the list because they are timely; others because they are timeless. You may not find a specific mutual fund or stock tip in the thousands of pages of reading material, but you will be equipped to make better-informed decisions for the lifetime of self-directed investments we all face. Here, then, is the course list for the Investing Autodidact. You don't have to read them all, but it would be a big mistake to not read any of them.