I don't understand why ours is a men's group. Look at the titles I mentioned. Women wouldn't benefit from these studies? I'd love to take my wife to them.
I guess it depends on the dynamic. Sometimes, and in fairness it's not necessarily very common, the social dynamic of a group of guys can change completely as soon as a single woman joins the group. I know a couple who are both very much into soccer (in her words she is something of a tomboy) and she always wanted to go to the men's events because they focused on sport while the women's events never interested her. But, of course, that particular group of guys talking freely were often prone to talk a lot less freely in the presence of a single woman. If you can get the group to continue to talk freely as a mixed group it's probably good to add the different perspective, I guess it depends on whether that particular group of guys would still work as part of a mixed group.
My church used to have a good men's bible study. It met on the 1st Saturday of each month. We would meet for a bit of fellow ship, eat a meal and then have a small Bible study. Basically we would read a section of the Bible and then discuss it. Then read on and discuss that. Usually went through 1 to 3 chapters a month (depending on how involved the chapters/discussions got). I think they started either in Gen. or Matthew. We had finished Romans and had started on the next book when we stopped.