Something

<head>
		<script type="text/javascript">
		function go()
			{
				box = document.forms[0].order_by_select;
				orderby = box.options[box.selectedIndex].value;
				if (orderby) location.href = 'index.php?order_by=' + orderby;
			}
		</script>
</head>

<body>
<?php query_posts('cat=4&posts_per_page=-1&orderby=' . $order_by . '&order=desc'); ?>
<?php if (have_posts()) : ?>
		<form id="order_form" action="index.php" method="post">
			<fieldset>
				<table>
					<tr>
						<td colspan="4" style="text-align: right;">Sort by:
							<select id="order_by_select" name="order_by_select" onchange="go();">
								<option value="title" <?php if ($order_by == 'title') { echo 'selected="selected"'; } ?>>title</option>
								<option value="date" <?php if ($order_by == 'date') { echo 'selected="selected"'; } ?>>date</option>
							</select>
						</td>
					</tr>
					<tr>
						<th>
						</th>
						<th>
							<h2>Title</h2>
						</th>
					</tr>

<?php while (have_posts()) : the_post(); ?>
					<tr>
						<td class="col_0">
							<?php if (post_custom('book_cover')) { ?>
							<a href="<?php the_permalink();?>"><img src="<?php echo post_custom('book_cover');?>" alt="pic" /></a><?php } ?>
						</td>
						<td class="col_1">
							<h2><a href="<?php the_permalink();?>"><?php the_title();?></a></h2>
							
						</td>
					</tr>

<?php endwhile; ?>
<?php endif; ?>
				</table>