php - SQL error when trying to update record in a database using PDO

I am getting the following error when trying to update a record in an SQL database...

Book not updated: SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'Adobe AIR (Adobe Integrated Runtime) with Ajax: Visual QuickPro Guide, bookYear ' at line 1.

Here is my code for the updateBooks.php file

    
    



// Retrieve variables
$bookISBN = filter_has_var(INPUT_GET, 'bookISBN') ? $_GET['bookISBN'] : null;

$bookTitle = filter_has_var(INPUT_GET, 'bookTitle') ? $_GET['bookTitle'] : null;
$bookYear = filter_has_var(INPUT_GET, 'bookYear') ? $_GET['bookYear'] : null;
$catID = filter_has_var(INPUT_GET, 'catID') ? $_GET['catID'] : null;
$bookPrice = filter_has_var(INPUT_GET, 'bookPrice') ? $_GET['bookPrice'] : null;

$errors = false;

if (empty($bookISBN)) {
    echo "
You need to have selected a book.
\n";
    $errors = true;

}
if (empty($bookTitle)) {
    echo "
You need to choose a title.
\n";
    $errors = true;
}
if (empty($bookYear)) {
    echo "
You need to choose a year.
\n";
    $errors = true;
}
if (empty($catID)) {

    echo "
You need to choose a category.
\n";
    $errors = true;
}
if (empty($bookPrice)) {
    echo "
You need to choose a price.
\n";
    $errors = true;
}
if ($errors === true) {
    echo "
Please try again.
\n";
}

else {
    try {
        //connects to database
        require_once("functions.php");
        $dbConn = getConnection();
        $bookPrice = $dbConn->quote($bookPrice);

        $updateSQL = "UPDATE nbc_books SET bookTitle = $ $bookTitle, bookYear = $bookYear, catID = $catID, bookPrice = $bookPrice WHERE bookISBN = $bookISBN";
        $dbConn->exec($updateSQL);
        echo "
Book updated
\n";

    } catch (Exception $e) {
        echo "
Book not updated: " . $e->getMessage() . "
\n";
    }
}
?>

Here is my code for the bookQuery.php file

    
    


All Books

try {
    require_once("functions.php");
    $dbConn = getConnection();

    $sqlQuery = "SELECT bookTitle, catDesc, pubName
                 FROM nbc_books
                 INNER JOIN nbc_category
                 ON nbc_category.catID = nbc_books.catID
                 INNER JOIN nbc_publisher
                 ON nbc_publisher.pubID = nbc_books.pubID

                 ORDER BY bookTitle";
    $queryResult = $dbConn->query($sqlQuery);

    while ($rowObj = $queryResult->fetchObject()) {
        echo "
\n
                   {$rowObj->bookTitle}\n
                   {$rowObj->bookYear}\n
                   {$rowObj->catID}\n
                   {$rowObj->bookPrice}\n
              
\n";

    }
}
catch (Exception $e){
    echo "
Query failed: ".$e->getMessage()."
\n";
}
?>

Here is the code for the form aswell

    
    



$bookISBN = filter_has_var(INPUT_GET, 'bookISBN') ? $_GET['bookISBN'] : null;


if (empty($bookISBN)) {
    echo "
Please choose a book.
\n";
}
else {
    try {
        require_once("functions.php");

        $dbConn = getConnection();

        $sqlQuery = "SELECT bookISBN, bookTitle, bookYear,nbc_books.pubID, nbc_books.catID, bookPrice
                 FROM nbc_books
                 INNER JOIN nbc_category
                 ON nbc_category.catID = nbc_books.catID
                 INNER JOIN nbc_publisher
                 ON nbc_publisher.pubID = nbc_books.pubID
                 WHERE bookISBN = $bookISBN";
        $queryResult = $dbConn->query($sqlQuery);


        $rowObj = $queryResult->fetchObject();

        echo "
        
Update '{$rowObj->bookTitle}'
        

            
Book ISBN 
            
Book Title 
            
Book Year 
            
Book Category 

            
Book Price 
            

            

        
        ";
    }
    catch (Exception $e){
        echo "
Book details not found: ".$e->getMessage()."
\n";
    }

}
?>