Page Chapter 3. Module-Specific Settings, Page 26

Location on the page: 
Last line of code
Error: 

'#default_value' => variable_get('annotate_deletion', 0) // default to Never

Correction: 

'#default_value' => variable_get('annotate_deletion', 0), // default to Never

Description of the Error: 

To adhere to Drupal coding standards, the last array element should be followed by a comma.

[That's true throughout the book. See my post here.]