1. Navigate to the ch4-book-reviews folder of the WordPress plugin directory of your development installation.
2. Open the ch4-book-reviews.php file in a code editor.
3. Find the call to the register_taxonomy function within the ch4_br_create_book_post_type function and add a new member to the configuration array named meta_box_cb with a value set to false highlighted in bold:

   'show_tagcloud' => false, 
   'meta_box_cb' => false,
   'hierarchical' => true

4. Save the plugin and edit a Book Review to see that the Book Type taxonomy box is no longer displayed.
5. Locate the ch4_br_display_review_details_meta_box function in the code and add the following code within the existing table rendering code to add a new row containing a drop-down selection box for the book type:

<tr> 
    <td>Book Type</td> 
    <td> 
    <?php 
        // Retrieve array of types assigned to post 
        $assigned_types = wp_get_post_terms( $book_review->ID, 
                              'book_reviews_book_type' ); 
                 
        // Retrieve array of all book types in system 
        $book_types = get_terms( 'book_reviews_book_type', 
                                 array( 'orderby' => 'name',
                                        'hide_empty' => 0) ); 
 
        if ( $book_types ) { 
            echo '<select name="book_review_book_type"'; 
            echo ' style="width: 400px">'; 
 
            foreach ( $book_types as $book_type ) {                 
                echo '<option value="' . $book_type->term_id;
                echo '" '; 
                if ( !empty( $assigned_types ) ) {            
                    selected( $assigned_types[0]->term_id, 
                              $book_type->term_id );
                }
                echo '>' . esc_html( $book_type->name ); 
                echo '</option>'; 
            }         
 
            echo '</select>'; 
        } ?> 
    </td> 
</tr> 

6. Find the ch4_br_add_book_review_fields function and add the following code segment within the if statement, checking to see whether the post type is a Book Review, to save the selected book type in the site's database upon the submission of the post:

if ( isset( $_POST['book_review_book_type'] ) 
     && !empty( $_POST['book_review_book_type'] ) ) { 
    wp_set_post_terms( $book_review->ID, 
                       intval( $_POST['book_review_book_type'] ), 
                       'book_reviews_book_type' ); 
} 

7. Save and close the plugin file.
8. Open a previously created Book Review to see the updated Book Review Details meta box containing a new drop-down list to specify Book Type: