Correct model associations

I am trying to bind 3 tables and I am having problems with proper relations. 

Table users (pk id), books (pk id), users_books (user_id, book_id), comments (pk and foreign key book_id, user_id -> with reference to users_books)

Here are the models:

Book

  public $hasAndBelongsToMany = array(

      'User' =>

      array(

        'className' => 'User',

          'joinTable' => 'users_books',

            'foreignKey' => 'book_id',

            'associationForeignKey' => 'user_id',

            'unique' => true,

        'conditions' => '',

        'fields' => '',

        'order' => '',

        'limit' => '',

        'offset' => '',

        'finderQuery' => '',

      //  'with' => 'UserBook'

    ),);

    public $hasMany = array('Comment'=>array('className'=>'Comment'));

Comment:

  public $belongsTo = array (

    'Book' => array (

'className'=>'Book',

    )

  );

When I try to save with the saveAll method I got: 

Error: SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`metabook`.`comments`, CONSTRAINT `comments_ibfk_1` FOREIGN KEY (`user_id`, `book_id`) REFERENCES `users_books` (`user_id`, `book_id`))  

I know that this is not according to the cakephp conventions, but what I can do to bind those tables?

--
Like Us on FaceBook https://www.facebook.com/CakePHP
Find us on Twitter http://twitter.com/CakePHP

---
You received this message because you are subscribed to the Google Groups "CakePHP" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cake-php+unsubscribe@googlegroups.com.
To post to this group, send email to cake-php@googlegroups.com.
Visit this group at http://groups.google.com/group/cake-php.
For more options, visit https://groups.google.com/d/optout.