I think it should be divided up into weeks. It paces people, I'm already 3/4 through the book and in a month Im not going to remember every detail and in what chapter it happened in! It gives us more oppurtunity for discussion too. What if someone is away at the end of the month? They miss out completely, and if it we had a discussion ever week they would be able to get to read a few of them. What about December when the discussion would fall on Christmas? or in the spring, when schools have spring break at the end of march and people go away?

It just makes more sense to me to do it every week or every couple weeks.