Drupal Advanced

No PHP knowledge required.
Goal: I was looking to display the list of all books in a node (and more generally trying to understand the design and logic of Drupal).
I'm using the book.module has an example, but this might also apply to all other modules.

I came across this good article: http://drupal.org/node/26502
The following is what I learned and extrapolated, from that article (read it first) and by digging a little further:

<?php
$block = module_invoke('module_name', 'block', 'Operation', delta);
print $block['content'];
?>
module_name: Is the module name.