Control unintuitive

I got a free book and the only way to download it is through this app. I have a 5s and it wont show me a screen of page by page, a few pages are squeezed together. And when I want to zoom in, it wont let me do it. I struggled with the app for 5 min and I still couldnt the book on my phone comfortably.

Beginner jogger about BookShout: eBook & Reading App, v7.4