The new Half Price Books location on Northwest Highway, across the street from their older, smaller location, is the mecca of cut-rate book buying. If you don't know what you want, you're bound to find 10 other books you didn't think of before. The music and arts sections are especially edifying, if not comprehensive, and they also boast a solid used-CD and LP inventory. If war is your thing, they have rows of Civil War and World War II books. You like mysteries? They've got tons of those. Political nonfiction your bag? It, too, has its own special section. A national company born in Dallas, Half Price Books should be commended for its strong continuing commitment here.