I've certainly heard of stranger business ideas that worked out.

I can only see this working out if it provides a friendly environment for readers to socialize in. The coffee may help, but you would need to go beyond that. Maybe you could provide a home for book clubs, pull in authors for readings, and anything else that you can think of that will both bring in revenues and negate the "but it is easier to buy it from the comfort of my home" mentality.

Another useful service would be the ability to browse a book from cover to cover on a broad range of devices. I have run into far too many books where the quality of the preview versions does not represent the quality of the book. (This is especially true for information books where the introductory chapters are very different from the bulk of the book.) And, of course, some books work well on tablets that don't work well on eInk devices. It would be nice knowing which prior to buying.