hi ,
first of all you tried the link :
www.yoururl.com/index.php?option=com_boo...amp;task=add_book_fe
is that correct?
second open the file booklibrary.php
and go to line 359 in booklibrary.php.
change this line : $clist = mosHTML :: selectList($categories, 'catid', 'class="inputbox" size="1" disabled="disabled"', 'value', 'text',$catid);
to this :
$clist = mosHTML :: selectList($categories, 'catid', 'class="inputbox" size="1" ', 'value', 'text',$catid);
it should work.