Now that Barnes & Noble and Microsoft have parted ways on a partnership to produce and sell the Nook e-reader, the book retailer is yet again faced with having to reimagine its business model for an increasingly tech-centric world. For inspiration, it should look no further than the coffee shops inside many of its stores, according to Wharton marketing professor Peter Fader . “Barnes & Noble doesn’t really know who its competition is,” said Fader, who is also co-director of the Wharton Customer Analytics Initiative . “It always thought it was Amazon or other companies that are selling books. competition is Starbucks. It should be a place for people to go and hang out and spend some quality time and learn a thing or two. That is where the money is to be made.” Fader and Wharton management professor Emilie R.…