mysql insert record from existing table with insert button - php

Question

Sorry if my english is not correct. I will try my best..
The question is how can I insert record from existing table with insert button. Everything work fine except variable $book. It records value 0 to database. Here is code..
//if the user press "INSERT BOOK" button there will be new record in database
<?php
$reader=$_SESSION['user_id'];
$book=$row['book_id'];
if (isset($_POST['update'])){
$sql = "INSERT INTO `read` (`read_id`, `book`, `reader`) VALUES (LAST_INSERT_ID(), '$book' '$reader')";
$result = mysql_query($sql) or die(mysql_error());
if ($result) {
echo " Yes, it works!";
}
else{
echo "noup!";
}
}
if(isset($_POST['submit'])){
if(isset($_GET['go'])){
if(preg_match("/^[ a-zA-Z]+/", $_POST['name'])){
$name=$_POST['name'];
$result = mysql_query("SELECT * FROM book b JOIN `read` r ON (b.book_id = r.book) JOIN users u ON (r.reader = u.user_id) WHERE b.book_name LIKE '%" . $name . "%' or b.writer LIKE '%" . $name . "%' AND u.user_id !=". $_SESSION['user_id']);
$num_rows = mysql_num_rows($result);
if($num_rows>=1){
echo "<table id='table1'>
<tr>
<th>book_id</th>
<th>BOOKNAME</th>
<th>WRITER</th>
<th>PAGES</th>
</tr>";
while($row=mysql_fetch_array($result)){
echo "<form action=add_book.php method='post'>";
echo "<tr>";
echo "<td>" . $row['book_id'] . "</td>";
echo "<td>" . $row['book_name'] . "</td>";
echo "<td>" . $row['writer'] . "</td>";
echo "<td>" . $row['pages'] . "</td>";
//echo "<td>" . "<input type = 'hidden' name = 'hidden' value =" . $row['book_id'] . " </td>";
echo "<td>" . "<input class = 'field' type = 'submit' name = 'update' value = 'INSERT BOOK'>" . " </td>";
echo "</tr>";
echo "</form>";
}//WHILE LOOP
echo "</table>";
}
else{
echo "NO RESULTS";
}//else
}//if(preg_match..)
} //if(isset($_GET['go'])){
} //if(isset($_POST['submit'])){
?>