I am not asking about right and wrong, but rather about whether directly addressing the customer's emotions is effective, if so how and why, and what is the purpose anyway. To get the customer just to go away? Or to go away satisfied? Or to make sure the store policy is upheld? It might not be possible to meet all of these goals. At the end of the day, the store will either exchange the book or not exchange it, perhaps making some other offer like those mentioned. This all seems separate from anyone's emotions. The final decision shouldn't depend on whether the customer is considerate or a real jerk; either she has a legitimate reason to exchange the book, or not.
I can speak only for myself, but when I go into a store, I know what I want, and would find someone's suggestion that I do not rather insulting. If store (or online) employees try to "make me feel better" with emotional talk, I tell them it is beside the point. I am there to get a problem resolved: what kind of accommodation can we reach? I suppose other people just approach these situations differently, warranting different responses.