This being Los Angeles, of course, most stores abound in movie star biographies, self-help guides and Buddhism. Automobiles and art books often show up in force too. Still, some proprietors are not sanguine about the future. They say that, with as many used-book stores as there are, many have closed in the last 20 years. They say that the Internet, while it has helped them move inventory to far-flung customers, has also driven off-the-street business, and even regulars.