When it comes to sales, it’s widely known that bookstores, particularly independent ones, face tough competition from online sellers such as Amazon. It looks like the battle lines just got tougher. With their new book app, Amazon is encouraging book store shoppers to scan titles they find intriguing, and see if they can get a better price online. The reward if you find a better price is the chance to earn five percent credit on purchases at Amazon, of course. This has some people up in arms. Among them is author and screenwriter Richard Russo, who wrote an op-ed about it in The New York Times. Russo won a Pulitzer Prize in 2002 for his novel, “Empire Falls.”