I have a community, how can I monetize it?

Hi. I have built a community by accident and am trying to figure out how to monetize it without a hard sell.

It's a reader community. Currently on FB. Very active with thousands of members, all driven by word-of-mouth. The whole thing is all about relationship marketing so I can't just throw squeeze pages at people (nor do I want to), I have to be really careful with how I manage this group. Right now I use it to sell my books and use my affiliate code for Amazon. So not a huge amount of money coming in.

I'm trying to figure out if I should try to start a mailing list (but I already have one for my books in that genre, so it feels like competing with myself--and I do market lots of books to folks all the time.) or migrate to a forum or what?

I'm not a marketer. This has all been a happy accident. I suppose I could charge authors for access, but then that hurts my ability to cross market my books down the line...see above re: relationship building<---that's my m.o. ETA: Authors are already active in the group. One thing I've done is funnel authors into a marketing group where we do cooperative promotion stuff so I do see some financial benefit from that, it's just not X dollars or month, it's more erratic.

This community doesn't have to be monetized, but if there are simple things I can do to optimize any income, I would love to know.

Thanks