It's quite unusual to see a company trade this far below book value, but a still-weak U.S. economy, coupled with deep distress in Europe, has many investors spooked about banking stocks right now. Citigroup ( C) is one of a number of banks selling below book right now. Yet as the storms clouds pass, shares of Citigroup are likely to trade up to at least book value (representing more than 70% upside). >>10 Bank Stock Value Picks Notably, Citigroup's earnings are depressed so that already-low P/E multiple will move even lower as the U.S. economy mends and Citigroup's results start to strengthen. That also means that book value will build higher, creating even more upside for this stock to work its way back to book value. Some analysts think that Citigroup, though it is one of the cheapest bank stocks around right now, has especially robust long-term upside. The bank has been investing heavily in South America and Asia which are home to a rising middle class, and a swelling number of millionaires. The bank hopes to ride the back of a rising explosion of wealth in those regions.