I noticed that some extra controls (including the book rating) appear when the mouse hovers the book... that probably won't be wise when you're dealing with touch-devices. I don't know about others, but I know that I only access the content server from my iPad... I don't need to access it from a PC.
So you should probably optimize the UX for touch-based devices (tablets, smartphones), so there will be a lot less clicking/tapping involved to see some basic book information.
Now I wonder, should the book's rating be displayed while you browse (as it is now), or only in the book details?
Also, do you have any plans to add proper support for hierarchical categories? Right now the web front end will display hierarchical categories by giving a flat listing of the its elements. I haven't really put much thought into what the best way to do that though...