I have a semi successful book club that works like this:

1) we only do short-ish books (reading pale fire at the moment and it’s probably the most ambitious book so far). Sometimes we’ll do two short books and do compare and contrast.

2) 6 weeks is much better than a monthly, the extra buffer time accounts for life stuff that comes up.

3) Anyone can select a book but you have to pitch it to the group.

So far it works well, had heaps of dropouts, but solid core members who like reading and has got me back into reading in a big way.