Do you parse every comment, and then look for book names?
The websites and Twitter feeds seem similar (and both seem great), was there any specific reason why you created an alternative?
I get most of my book recs from HN comments. Usually they are non-technical, anything from Michael Mauboussin to the Secret Life of Groceries. I would appreciate a simple "coreHN / not-coreHN" switch. (CoreHN would be books about startups, technologies, etc. I prefer the diverse topics, which are often buried in HN).
Also curious - are you parsing comments to identify books, or just submissions?
I like the coreHN / non-coreHN idea. The search page [0] has links to categories that can allow you to dig into the different categories of book recs a bit but you still need to parse out which categories are core vs non-core.