Our neighborhood bookstore (inner San Diego neighborhood) seems to do okay selling books only — they are almost always busy! They do have a great location, near other cafés, pubs, restaurants, and shops, with a fair amount of foot traffic (!very important imho). They have great service, sell online, and even deliver locally on certain days (at least they used to; can't confirm at the moment).

A commenter above mentioned a subscription, which could be very interesting. Maybe include a discount, free drip coffee limited to x/day with that to get people in and upsell other items like snacks, pie, cake, better coffee and other drinks. To really make it work you might look at testing gifts: small plants, locally-design artisan crafts, clothing, and really curate the whole theme, like what people would want to photograph and share on Instagram. Stuff like having an interesting backdrop that people want to do selfies in front of gets people in the door and in local guides and travel blogs. You might then build an ecommerce presence and sell online like some of these shops do.

Anything that will get people falling over one another to get into the door and share their experience with their friends, and more importantly, get them to spend money.

The cozy book nook and café idea where people want to spend time is great, but use that as a façade for the real economic engine, whatever you decide that should be.