Bookstore sales rose 0.8% in May, to $1.2 billion, the second month in a row that store sales increased less than 1%. Sales for the entire retail segment increased 2.4% in May, according to the U.S. Census Bureau. For the first five months of 2002, bookstore sales were up 6.8%, to $6.67 billion, slightly more than double the 3.2% gain posted by all retail outlets.