The comic book club sounds cool. I don't see anything wrong with featuring longer stories like 100 Bullets at times, but you would probably have to limit it to the first trade. People who enjoy that can pick up the rest if they want. The podcast Comic Geek Speak used to do a book of the month club when I still listened to them. I liked how they would rotate their focus depending on the month. Like, month 1 was Marvel, Month 2 was Independent, and Month 3 was DC. Maybe do something like that, but make it even less big 2 superhero focused?
Like:
Month 1 - Superhero (Marvel/DC or Creator Owned)
Month 2 - Crime or Espionage
Month 3 - Sci Fi
Month 4 - Horror
Month 5 - Fantasy
Month 6 - Miscellaneous
People would need time to buy the right book, so I would make it either monthly or bi-weekly.
If you want some suggestions for non-superhero stuff, I'd recommend Queen and Country, Scalped, Essex County, and Lone Wolf and Cub. Some of those may be out of print though.