If the print in a Caribu book is too small to read, you can use two fingers to pinch and zoom in to a location on a page. This will only zoom in your screen. If you want to return to the full screen, simply tap the screen twice for Apple devices or pinches your fingers back together on Android devices.
Some devices allow you to turn it horizontally. This also depends on the device your contact is using as well. That could widen the view of the book and allow you to see more clearly.
If that does not help, try adjusting the brightness settings on your screen or the lighting in your home for a more illuminated text.
Using Caribu with a tablet or iPad will provide larger print overall. If you have trouble reading text on your phone, download the Caribu App to your tablet or iPad and use it for your next Video-Call.