Is it right to read half a book/magazine at the store and not pay for it?

I went to Barnes and Nobles Shreveport today and something is happening there. All the oversize please-flop-onto-me armchairs are gone.  Several units of long-span shelving are up with some children's toys starting to load on them. The benches by the magazine section and aroma-contributing Starbucks are still there though.
I wanted to scan through a book at the coffee shop but there was a group of people holding some serious meeting there, sounded serious because everyone else was quiet listening to one guy monologue. Those benches were too high for me and reading with hanging legs just don't fit the profile of a over-the-hill person. So I decided to stand by the aisle and read.
It was so interesting that I finished 100 pages (almost half the book) in less than 2 hours. Then something unusual happened. I felt guilty. Somehow I have convinced myself that they removing the super comfy armchairs is a result of making losses and therefore, they need to display for merchandise and sell more stuff. So I decided to pay for what I read which was $17 of it.
When I came home and check on amazon, it only cost $10 if I had it ship to my house in 2 days. Plus it is only a 3 star rating and there were many more higher rated ones. Now, I am tempted to bring the book back and ask for a refund and purchase something else on amazon. But it just doesn't seem right that I walk into their store, read their book and not pay for it. Even when they are not competitive, I feel the need to support their business. Do I really want to see another book store close down? And then I would have completely no where to explore and expand my mind while waiting for 2 hours. What do you think?