YouIf you are creating the form youself, you should be able to do something as simple as this:
$form['YOURFIELDSET']['captcha'] = array(
'#type' => 'captcha',
'#captcha_type' => 'captcha/Math',
);
where 'YOURFIELDSET'
is the Submit Your Book
fieldset. (Just don't have the Captcha automatically add it itself.)