The blog did not update over the weekend because of a power outage at UCSD. (http://www.nbcsandiego.com/news/local/Electrical-Fire-Sparks-at-UCSD--154546705.html).
I also changed the update schedule from 5:55am PST to 5:55am PST *and* 1:55pm PST. Since the Amazon top listing is supposed to be derived from some time weighted average of sales in past hours, the list of book appearing in the afternoon might differ from those appearing in early morning.