Bookstore sales had their worst month of 2010 in September, with sales down 7.7%, to $1.51 billion, the U.S. Census Bureau reported this morning. The September decline follows a 6.5% drop in August and resulted in a 2.6% decline in bookstore sales, to $12.31 billion, for the first nine months of the year. For the entire retail segment, September sales were up 7.6% and nine month sales increased 6.3%.