Unfortunately CookBook is mostly intended just for storing your recipes on your app and creating your own personal CookBook, not as a physical cookbook creation tool.
We have added this request onto our ideas list however at the moment it is not something that we are looking to implement.
You do have the ability to print recipes in a .pdf format however this is one by one so you would have to piece together the physical cookbook yourself.
You can bulk export your recipes into HTML format inside a zip. Whilst these are not formatted for print, you might be able to print them into a single document on your PC, format them in a way you would like and get them printed into a physical CookBook. Find out how to bulk export here.