I say combine the two but if I had to choose one or the other at first thought it would probably be a coffee shop. I think that it would be more economic to own a coffee shop. I'm not completely sure of the statistics but I would venture to say that more American's drink coffee than read books.
Also with the introduction of eReaders the future of bookstores is in jeopardy. It is uncertain if the bookstores that are already out there will be able to survive the coming decades. Therefore, I believe that people will always want to enjoy a gourmet cup of coffee prepared by someone else and buy there books online.