Hi kepa,
thanks for reporting, but on that file (row 81) I see this code:
$lists['file_path'] = JHTML::_('link', 'images' .DS .$params->get( 'file_path').DS.$book->file, $book->file);
Try to put this code in your file and you see if you like the result.
This is the html output:
<div><strong>file: </strong><a href="/images/file_path/file_name.ext">file_name</a></div>
Bye bye