There's enough material on the web at this point that a list of other peoples lists and personal collections probably has more value on average than a news aggregator.
The strategy this implies is going a further level up, which implies going a further level up, etc etc.
EDIT: I changed my mind, but don't feel like going into detail here. The problem with these lists is that there's a lot of repetition. If everybody would list their books in the same format you could get rid of the repeats and leave only the books that have been recommended by a HN member. Bonus if you can put the descriptions into a structured format as well.
I agree that it would be nice to have this nested (meta-)lists on a service that would treat them as sets, merge them together and as a cherry on top would show you the overlaps.
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Hacker News stories which contains plenty of book recommendations (sorted by points, labeled by topic):
Science Fiction: http://news.ycombinator.com/item?id=2978027
Computer Science: http://news.ycombinator.com/item?id=3595599
General: http://news.ycombinator.com/item?id=1752139
Design: http://news.ycombinator.com/item?id=3276986
Computer Science: http://news.ycombinator.com/item?id=1636275
Developing mental models and increasing cognition: http://news.ycombinator.com/item?id=3277457
Quant finance: http://news.ycombinator.com/item?id=3177815
General: http://news.ycombinator.com/item?id=663662
General (non software): http://news.ycombinator.com/item?id=1226736
Math: http://news.ycombinator.com/item?id=665029
General: http://news.ycombinator.com/item?id=875686
Entrepreneur: http://news.ycombinator.com/item?id=2928211
Statistics: http://news.ycombinator.com/item?id=902074
Philosophy: http://news.ycombinator.com/item?id=1503137
General: http://news.ycombinator.com/item?id=1865350
Math for beginners: http://news.ycombinator.com/item?id=755043
Military strategy: http://news.ycombinator.com/item?id=456275
General: http://news.ycombinator.com/item?id=797070
Investing: http://news.ycombinator.com/item?id=248469
"I want to start a web company": http://news.ycombinator.com/item?id=1567456