/*
---------       ----------
| Books |       | Author |
---------       ----------
| id    |   --->| id     |
| name  |   |   | name   |
| a_id  |----   |        |
---------       ----------
*/

//Model_Books.php
public function fetchAll()
{
    $select = $this->select()->setIntegrityCheck(false);
    $select->from($this->_name, array(/.. your columns from books/))
           ->joinInner('books', 'condition', array('your columns'); //or you can use $this->_referenceMap

    return parent::fetchAll($select);
}