Hadrien, I noticed that I am able to get many feeds with full content using Mobipocket Reader but when I tried using Feedbooks I only got partial feeds. The problem, I think, is with the URLs. For example, if you use the following URL for Time - Most Emailed Articles:
http://feeds.feedburner.com/time/mostemailed
you get full content in Mobipocket Reader. when I paste this URL in Feedbooks, it dynamically updates the URL to something which only has partial contents. This is also true of many other feeds (WSJ, NYT, Google News, Slate etc) for which I am able to get full contents using Mobipocket Reader
but Feedbooks generates only partial feeds. I wonder of there is a way to fix this.