Smaller stores (In shopping areas as opposed to a bookstore set apart from businesses, requiring one to travel expressly for the purpose of visiting said store) would increase visibility and encourage visits. Netflix contributed to Blockbuster going out of business but people still dig through the DVD bins in their local supermarket.
Also, I thought B.Dalton and Waldenbooks complemented each other well. This was back in the late 90s so I obviously don't have as much experience as most of you but I seem to remember B. Dalton having more non-fiction and Waldenbooks having the fiction. Maybe they didn't have all the books but I guess they were the only stores I had before I moved to a big city and I could always find/order anything I wanted. There was also a used bookstore in the older downtown shopping area outside the mall, about a block away. Between these three stores and the library I never felt like I was missing out on anything.
Of course it doesn't compare to my first trip to San Francisco, going to Berkeley and having an entire street full of used bookstores. It's a good thing I didn't have bills in those days