I've been thinking about your various challenges, and I keep coming back to the layout of your shop. I think that you can guide your customers to act the way you want them to by where you place them in your store.

For groups, consider have a special area for them. Maybe take sign-ups for book clubs to meet in a designated group area. In other areas of the shop, don't put the seating in groups, just have places for single people to read.

Other thoughts... do you charge for coffee refills? If you have free refills, that would entice them to stay longer and just keep filling up their cups.

Do you have a frequent reader card? Encourage your customers to purchase books with incentives for repeat purchases. For the ones who are there reading in and drinking your coffee, offer a drink discount to those who purchase a book while they are there.

If book sales are your money maker, focus on getting the word out about your books. Have a newsletter or blog about new releases, as well as a sign in-store. If it is coffee that makes your money, offer book discount coupons to your coffee drinkers to entice them to buy more books. Basically, cross promote your books and coffee as best you can to encourage every person in your door to buy both a book and coffee.

One thought I had about your customers who come in to read without buying anything-- maybe a two drink minimum for customers who don't purchase a book but bring their own or read one of your used copies?

I'm just brainstorming here and typing my train of thought, so I hope this is helpful! Have a great evening,