Lisa -- Our group started from a cluster of parents whose kids attended the same school. We got to know each other from various school activities the kids were involved in. When they graduated from high school, we decided to stay in touch, and that's how the group started.
The group picks the discussion topic for the following month. For example, last Saturday the topic was "choices." We talked about choices made, and their outcomes, and also choices we plan to make. Last month the topic was "Taoism." There is no set pattern to the topics, and it's fun and interesting seeing the various topics we've discussed over the past 3-plus years.
We meet at our home because there is a room set aside with couches, chairs, pillows, and fireplace. Everything is very informal, and people come and go to the kitchen at anytime for snacks, wine, etc. It's not unusual hearing people in the kitchen continuing the discussion there. When everyone is there (which is usually the case) 9 attend.
The group is very diverse, which adds greatly to the discussion and fun. Some are people of faith, and some are not. All in all, it's the best bookstudy (usually without books) I've attend and had in our home.