The app seems to have trouble loading content in the categories I checked. The content is pretty poor. Mostly Project Gutenberg free public domain books. You should open your doors to indie authors. The times are changing and a lot of good authors are going independent and avoiding the publishers. Your bias will hurt you as right now you have an app with books that we can get anywhere else for free. Why would we read Jules Verne here with ADS in it when I can download it to iBooks. There are indie authors that would fill your categories with novels.
Acketon about 24symbols – online books