Well the way I've done it with my club is we got a whole selection of books that people suggested. Some had read them but were willing to read them again, some had heard great things about the books they suggested, and some owned the book and wanted to read them.
The way we pick is whoever hosts the meeting gets to pick the book for that month. Sometimes it's a book that you think you might not like or have read before, but it's a good way to get exposed to knew authors. And if you have read it before, this gives you an opportunity to discuss it and perhaps get a new perspective on it.