Of course, you could always advertise for book club members on Mumsnet.
That's how I joined my book club, when another MNer suggested one in my area. 3 of us are Mners, a couple more are friends of friends. It's been going well over a year now and it's great.
A couple of people have come and gone but I think there are now 7 regular members, which seems just about the right size.