FYI: All figures are expressed as year-to-date. The AAP did not offer data specific to the month of November and simply subtracting the reported figure for October 2012 won't work because it results in bad data (here's why).
But the important news today is the ongoing success of ebooks. The overall US ebook market (including adult, children, and religious) was worth $1.4 billion in the first 11 months of 2012, and that is up 44% from $994 million in the same period of 2011. As a combined total ebooks were about 22% of the total US book market in 2012.
According to the AAP, their members are reporting that the adult ebook segment accounted for $1.15 billion dollars in the first 11 months of 2012, up from $858 million in the same period in 2011. Children's ebooks grew even faster, to $222.3 million from $92.3 million in 2011. And religious ebooks also increased to $53.4 million from $43.4 million.
A glance back at the AAP report from October shows that growth may have slowed. The first 10 months of 2012 demonstrated a growth rate of 46%; factor in November 2012 and it's now 44%.
While some might suggest that growth has slowed, the difference might also be explained by a few publishers updating their balance books and resubmitting the updated data to the AAP. Or they could simply have supplied data containing errors which were later corrected.
I don't plan to read anything into the month to month differences; I don't have the data needed to place them in context.