I've tried using it, but I find the interface too "life like", too much like a book and a book shelf. I would rather that it was designed more as a tablet application, I believe it would be more effective to use.
Also, it won't display in portrait, only in landscape which make the interface take up unneeded space when reading the texts.
I just ended my Kingmaker campaign, and if we start up a new one I will try this out more properly.