I'm part of a club that reads a chapter every week and meets to discuss. Our club is small, and most of us are well read in this particular genre. We start by discussing general impressions, things we liked/disliked, before we move into discussing specific passages and the implications of them on the larger picture. Because most of us have read around quite extensively in the genre, the tail end of our conversations is almost always a comparison between our current book and how it measures up to other titles.

It's great you took notes, because this gives you something to bring up or talk about. If you ever find you don't know what you should be taking notes on, you can Google around and look for discussion questions for your book. A lot of popular titles have blogs where they have a few questions, or honestly if it's a classic, Sparknotes has a few discussion starters or entries on symbolism that may get you thinking.

Since it's a larger group, I bet they likely have someone who is going to start and steer the discussion. This might make it easier for you to contribute if it's more structured, and the amount of people is great because you'll get a lot of varied viewpoints that make it interesting. Don't panic if you don't immediately feel like you fit right in with the book club. Sometimes you have to go to a few meetings before you hit your stride and feel comfortable with the process and group.