There's a visual bug in regards to using the search within a book in the new app.  It lets you search, but there's no text bar (which used to display at the top in the old reader app) to see what you're actually typing. This makes typos a bit of a pain.  Same on both my android phone and tablet.

note: when you access the search feature from the main page, it does show the entire background image, and the search bar at the top. Of course, then your search is searching every installed source. The search from within the book seems to push up the background when the keyboard comes up, and cuts it off, I'm wondering if that's what's causing the search bar to disappear too.