As price wars dip into already slim profits, offering an array of gifts and other non-book products with impulse purchase appeal can make a significant difference in a bookstore's bottom line this holiday season. Here's a look at some popular items selling well at three indies whose owners take serious advantage of the excellent margins offered by non-book products. Just don't call them sidelines, Steve Bercu, owner of BookPeople in Austin, Texas, cautioned. "I will point out that BookPeople does not sell any sidelines.