Poor Charlie's Almanack. It's a compilation of talks and essays from Charlie Munger, Warren Buffet's business partner. This book has single-handedly changed my invest strategies and mindset. Instead of trying to buy low and sell high, Berkshire Hathaway holds a large cash position, until they find something they consider to be a sure bet, take a large stake and hold. I now have the quote "Be right and hold tight" written at my work table.