One of the problems with the manga discussion is since each manga is in a thread, and people don't have the opportunity to discuss the topics seperately it tends to degenerate. Having a seperate minor forum, or a child forum for just the series that are being read by the book club like effort would fix some of that; that way the different topics of discussion have a place to separate out and not get congested. Another idea is to either separate genre's or to actively describe the genre's of the series in the description. A lot of the descriptions are pretty misleading if you don't know what the genre is. It isn't obvious from Mx0's description that it's an action/fighting heavy manga. Just a thought, since I know I overlooked a lot of series because the description made me misidentify the genre and only because I got bored this summer did I end up reading any of them.
Also picking series where there actually is something to discuss helps.Mmm, that's not to clear; I mean non popular series might be interesting to read, but for them to constantly generate speculation and discussion requires they have a certain degree of sophistication in the way they build up and portray themselves so that serious discussion on ideas where there can be a genuine difference of opinion can occur. Naruto is so popular that there's tons of speculation but a series like Death Note, which while popular isn't exactly mainstream can consistently produce an equal or greater amount of meaningful discussion, course the big problem will be finding a vocal and interested enough minority who are willing to read such plot and thinking heavy series. [Edited to add genres idea]