Hi Philip,
you can change the word "Review" by language override (using another word or left blank for COM_ABOOK_REVIEW) or hide that h3 tag by css.
Otherwise you have to delete line 347 of components/com_abook/views/book/tmpl/default.php (abook 3.1.5)
<h3><?php echo JText::_('COM_ABOOK_REVIEW');?></h3>
But I suggest to use template override instead modify original file