I belong to a terrific critique group (writing group) that has dealt with a lot of attrition. We started with 6 people and currently have 4, one who joined after the first month or two. We also had another new person that didn't work out. Some people weren't a good fit but others left because they moved or got too busy to write.
We decided it works best for us to meet once a month and have 3 people present each time (instead of the 2 we've done lately). So we've been looking for new people to join us. And someone will be joining us this month!
We communicate on an email mailing list where we discuss logistics only and also post our work several days in advance of the meeting. The meetings themselves are at a member's home and last 1-2 hours, depending on the number of presenters and how much time each gets. This includes schmooze time. Each presenter reads all or part of their submitted work (depending on length) then everyone talks about it. Each presentation runs about half an hour, give or take.
It was easier with the other newcomers because they could catch up, but now all but one of us are very deep into novels, presenting 1-2 chapters every other month. If the newcomer starts in the middle she won't know what the heck is going on, who the characters are, how they've changed, etc. I'm not looking for proofreading. I'm looking for folks who will tell me how my plot is unfolding, if the characters seem true to themselves, etc.
How do we make this work? Do we require the newcomer to read 3 half-novels? Do we just accept that she won't be able to give substantial critique? We're happy with the group in every way except that we need to incorporate a couple extra members.
How can we keep our group both welcoming and effective?