Marty, This app is great! I bought it today to use on my win8.1 tablet.
Until now, I have been running Calibre on my desktop and pushing books to either a Kindle 2 or an Android tablet.
My biggest gripe with the Kindle (and the Kindle app in Windows) is that there is no easy way to read the book descriptions without going to each book page on Amazon. I can get the description and a lot of other info on the Android tablet by using the Calibre Companion app, but I would rather just use the Windows tablet where I do my other windowy stuff.
As far as feature requests...
In Calibre, I have a custom YesNo column called Read which I set once I have finished reading a book. I also added it as a Virtual Library for #read:false that shows up as a tab at the top of Calibre. Do other users have something similar? It would be nice if I could filter the books in Calibre Viewer to hide the ones I have read.
A way to re-size the cover image and/or description section (seeing the book descriptions is my favorite feature
The ability to tap on the "Tags" label to switch between Tags/Series/Authors
A cover browser or cover grid view (like in Calibre) that just shows larger cover images with the highlighted book title/info/description/etc in a (re-sizable) section to the right or below.
Thanks!