Interesting, solves a problem I have. Although as I do not live in the US, I don't have it often.
I wouldn't include books at all in the lists. When I want someone to help me discover great products, I don't think about books. You will have a strong bias for the taste of your current visitors and also there are other, better ways to discover books.
But to discover a "water garden fish tank" that's the problem I have.