I think every good customer experiologist should have read Why We Buy by Paco Underhill by now (it was first published in 1999). The subtitle, "The Science of Shopping," explains why: it's all about understanding what is really going on when customers shop in a physical retail environment, based on mountains of detailed observational research.
If you haven't read it yet, well--I'm right there with you. I've decided this is a deficiency I need to correct, so I'm digging into the book right now. I'm only through the first four chapters. So far it's more about how we shop than why we buy, but the myriad illustrations are driving home one clear point: details. So many details influence what we do and how we do it in a store. Said in customer experience language, the nature of customer experience in a physical space is governed by many small details; if you want to optimize that experience you're going to have to go granular.
One quick sample from the book: the "butt-brush effect." Bloomingdale's in New York had a tie rack on the main aisle near a ground-floor entrance. During busy times, shoppers would approach the rack and start browsing, until they had been bumped once or twice by other shoppers moving in and out of the store. Most of the tie browsers would abandon their search. Underhill concluded that shoppers--especially women, but also men to a lesser degree--don't like being brushed or touched from behind, and they'll quit their shopping behavior to avoid it. Bloomingdale's repositioned the tie rack and voila--sales from the rack went up quickly without making a single change in the merchandise.
That's a customer experience victory: improved shopping experience and higher sales.