I shop here first because the service is first rate. If they don't have the book I'm looking for they can get it and often at a competitive price. Their Web site (http://www.leebooksellers.com/NASApp/store/IndexJsp) is easy to navigate too.
Locally owned bookstores are becoming more rare so I prefer to support a local business before going to a national chain. The selection at the large stores is, obviously, tough to beat. But you'll be suprised at the selection at Lee's. And the service is better than you'll get anywhere.
If you know what book you want, compare prices. I'm sure you'll find Lee Booksellers is competitive in price and superior at customer service.