Surely the 'Recommendations for Your Favorite Book Genre' thread could be considered as 'Reference' as the material in it doesn't date .....
Each of the genres listed contain a wealth of material that can be added to ad infinitum. And, as new genres appear on the market they can be added. (Say like 'steampunk' is fairly recent (and it does have a listing)).
The interested member can view any of the categories and get ideas for their next read, and/or they can add their author/book to a genre. A member doesn't have to make a contribution for this thread to be useful.
I think that this overarching thread should be a permanent 'sticky' in the Reading Recommendations Forum, it serves as a very useful reference.