Sounds like the problem is that your sample size is too small. What happens if you expand the timeframe out to a month? Or a year? That should give you books that are cited repeatedly, not just the books which have recently been mentioned by high-karma HN users.
Agreed. Monthly seems like a much more natural timeframe for book recommendations than weekly. Trailing 30 days would probably be the best for the homepage. Then allow browsing by calendar month.
