How to sell comic books through Apple in-app purchase?
Apple thoroughly documents the requirements for participating in their stores at the developer website:

https://developer.apple.com/resources/

You should review the iBooks and In-App Purchase from the above page.

At that point, you should be ready to read and digest the actual App Store Resources themselves to figure out what sort of effort you'll need to expend to sell your content through Apple.

https://developer.apple.com/appstore/index.html

Assuming you are on iOS - you can skip the parts on the Mac App Store. The review guidelines have some of the information you'll need.