Last January, I started to focus my attention on the site and posted more review articles. It was hit by Penguin last February until May and sales had dropped dramatically when every pages disappeared from Google pages. I managed to manipulate the content and starting late June, sales goes up again.
It's August 30 now and this is so far my biggest Amazon month when the site sold more than 300 covers and a dozen of kindle devices plus a number of non related products ranging from dildos, books, toys, even power tools, and even fitness equipment (the most expensive non-related product it sold).
This year, my plan is to create a big site dedicated only to selling amazon products in almost every category. I tried several amazon wordpress theme during my trial and error, but most of them uses wprobot so they are not for me. 100% of my reviews are unique and using any robot would only hurt my SEO.
Although the listbuilding is somewhat irrelevant when running an Amazon review site, the result is hard to imagine when it's already happening......
To those who says Amazon is a waste of time because of small % commission, I strongly suggest you try before making ridiculous comments.... I just realized this after reducing my commitment with Adsense.