my friend and i have one. there are about 12-14 of us though not all of us always show up. we do a big order from amazon and order the next 4 books we're going to read at a time.
it started with about 4-5 of us wanting to have a book club and then friends of friends heard about it and wanted to join too and it grew.
we're supposed to get together every month or so but really it works out to once about every 6-8 weeks. each time someone offers their house and they can either cook something or potluck and we all contribute. and we always get very drunk.