Barnes & Noble might be pushing the Nook as hard as it can, but the retailer has always said it wants to build a reading platform across devices, and it's making a big step in that direction with the launch of its eReader for iPad app today. The app allows Nook users to download most of their content to the iPad -- the books all work, but some periodicals like the New York Times and Wall Street Journal aren't available yet -- and there's a nice bookshelf view with jacket art and a
