Authoring guide

In addition to reading the manual, I would recommend setting up an author account on Leanpub and checking it out before you get too far along. The books I am working on with Lonnie and Kenji are written in Markdown, with a mix of inline code snippets and imports from PHP files. For me, it's only slightly different from working on Bonfire's documentation or writing a comment on GitHub, and being able to do something like this to add a code snippet is pretty sweet:

Code:

{line-numbers=on,crop-start-line=10,crop-end-line=25}
<<[Title Of Code Snippet](code/MY_Controller.php)

Very few people would want to see code as it's displayed in my editor, and it isn't optimal for print, either. Additionally, an image of text doesn't work well when you need to make it available in multiple paper sizes or on mobile devices (it would also be difficult to make an image accessible to users with vision problems).

Bonfire

Practical CodeIgniter 3
CodeIgniter Testing Guide