Developing a custom eBook Reader for iOS

I'm looking to create an eBook reader but I'm having some trouble finding the best path forward.

Currently, I've loaded an rtf file into an NSAttributedString and assigned that attributed text to a UITextView to create a long scrolling format.

I would like to have the format more like traditional eBook reader apps that create pages that you horizontally swipe.

I'm uncertain that best way to chop up the text into pages that I can scroll horizontally. Is this something I need to compute myself or is there any built-in functionality in iOS to assist with this process? Is there a better format I should be using instead of rtf like epub?