On this tangent, I wouldn't suggest premium features, unless they're minor because they tend to tear apart communities (look at all the games). I'd suggest nonintrusive ads and/or affiliate links to books, which would fit this site nicely. You could also put a store in there selling things relating to these topics, either setting that up yourself, or again going the affiliate route. Honestly, you could just look into how similar sites are doing their financing, and see what you can copy from their methods.