Beginning of december though, was the GOOD time to harvest, just before the Christmas season.
Enter the KDP Select program, in which indie-publishers can enroll individually (and for a renewable duration of 90 days) each of their book.
First, the author gets 5 "free days", during which he can set the price to "free". While it may seem a bad financial move, going free for limited time has often proved to have good results in generating reads, which generate reviews and recommendations, which generate additional sales either when the book is off-free, or on other non-free books by the same author.
Secondly, Select enrolled boks are put in the "Prime" library, which means they can be burrowed for free for "Prime" customers, at most one at a time. Some direct "money compensation" is done through a fund, divided between the authors depending on the total number of borrows, and each author's books. With the program's success, we can now know that this financial compensation should be at best symbolic, but it's not the only compensation for the author : the borrows/lendings are taken into account by the ranking algorithm. This means that the more a book is borrowed, the more it climbs in the ranking, hence the more it is borrowed, but also bought by the non "Prime" customers. This seems to largely compensate for the dollars loss. As a nice side effect, it also adds value to the "Prime" membership, by giving them access to a greater number of titles.
Last, the author/publisher gives exclusivity to his book for the entire 90 days duration. Which means that "established self-publishers" not only lock themselves to Amazon, but also attract their followers in their wake. These new customers, will of course discover other self-publishers, buy from them through Amazon, augmenting Amazon's share in their revenue, and finally prompting them to subscribe to Select.
Additionaly, by asking for the exclusivity, Amazon ensures that books will be designed primarily for its Kindle platform, and as a second thought for the other ones. Once an author has put it's book exclusively on Kindle Select, he will be less inclined 90 days later to start formatting anew for the other platforms, especially if he had good results on Kindle.
These 3 effects combine to create a "virtuous" (for Amazon) cycle, that attracts authors, who attract customers, who attract authors ...
How has it worked, so far ?
Well, from what I see at the KindleBoard's Writer's Cafe, where a great number of self-published authors spend some time, the big majority of those who made more than 70% of their sales at Amazon went "Select" for at least a few books. And those who DID go Select, have done so with (so far) gret results, getting more visibility, and climbing the rankings.
I can direct you to Kevin McLaughlin's Early Evaluation of KDP Select Program post to show you how it all went... Basically, Large Publishers are toast, Indie get a BIG visibility boost.
As an other result, some of the authors I like are going exclusively Amazon, and since I decided to not buy there ... Poor me !
For those who decide to go exclusive, I'd suggest something though : What if you planned ahead, twice a year, a 5-10 days of "No Select" period for all your books ? You could put them for sale directly on your website, in epub format, so that us, non "Kindle" owners could buy and read them ?
Update : a list of links to Author's blogs about this (on their blog, or forums)