An international chain, as they have a few locations overseas.
They revolutionized the marketing of used books through the simple and common sense solution of organizing their stock, making their aisles wide enough to walk through, and having good lighting. All of the things you would expect of any new book dealer but none of which were typically found at traditional used book dealers. They created a pleasant environment and gave their customers a very good chance of finding something from either the author or genre they came in the store looking for and made it easy to browse. Traditional stores typically have their stock jammed in any old place, sometimes "double parked" two deep on a shelf, and frequently stacked up knee-high on the floor of their already impossibly narrow aisles. Finding something that appeals to you is purely a matter of serendipity. Going in search of a specific title is somewhere between looking for a needle in a haystack and a fool's errand.