Once you’ve decided on the ideal size for your reading group, you’ll have to decide on the make up of the members.
Do you want a group composed of both males and females or just females? Your choice might, not certainly, but might, have some bearing on the books you read. And, while some groups want "all female" input, others value the input of both sexes.
Would you like all your members to be under thirty-five or over sixty-five? Again, this could have a bearing on the books you read and the input your receive.
A group composed entirely of stay-at-home mothers of preschoolers will probably be reading very different books than one composed of both men and women of differing ages and occupations. The composition of your group will also be a deciding factor when choosing a meeting time and meeting place. Stay-at-home moms, for example, will probably prefer to meet during the day, while most working people would find that impossible.