The two buttons I was talking about are the ones in the bottom left corner of the screen. The page number and zoom that you cannot click at the moment on in order to go to a page or change zoom. Take a look at the picture, it shows where they are(sorry about the logo on top of them):
The next thing is zoom, it is a bit confusing. I can only change it to zoom in but I didn't understand how to confirm it. I just pressed one of the buttons to get out of the zoom options. Maybe you could change it so that one hardware button zooms in, the other zooms out and a confirm or ok button, or the way it is in pdfviewer with several zoom option buttons(100%, 120%... custom zoom %). Then the choice between zoom and columns could be done by touch.
The other thing is that it is limited to 195% zoom max and it is a problem for scanned books. I will attach a file so that you could understand what I am talking about. This attached book has two pages on a view and when I switch to 2 columns it automatically changes to 200% zoom but if there was a need to zoom in more you can’t.
The example book