<?php
/**
 * post-process.php
 * make sure to include post-process.php in your functions.php. Use this in functions.php:
 *
 * get_template_part('post-process');
 *
 */
function do_insert() {
    if( 'POST' == $_SERVER['REQUEST_METHOD']
        && !empty( $_POST['action'] )
        && $_POST['post_type'] == 'book' ) { // Check what the post type is here instead

        // Setting the 'post_type' => $_POST['post_type'] in the $post array below causes 404
        // Just set it based on what is set in the above IF $_POST type == 'book'.
        // and below do 'post_type' => 'book'

        // Do some minor form validation to make sure there is content
        if (isset ($_POST['title'])) { $title =  $_POST['title']; } else { echo 'Please enter a title'; }
        if (isset ($_POST['description'])) { $description = $_POST['description']; } else { echo 'Please enter the content'; }

        $tags = trim( $_POST['post_tags'] );
        // Get the array of selected categories as multiple cats can be selected
        $cat = array( $_POST['cat'] );

        // Add the content of the form to $post as an array
        $post = array(
            'post_title'    => $title,
            'post_content'  => $description,
            'post_category' => $cat, // Usable for custom taxonomies too
            'tags_input'    => $tags,
            'post_status'   => 'publish', // Choose: publish, preview, future, etc.
            'post_type'     => 'book' // Set the post type based on the IF is post_type X
        );
        wp_insert_post($post);  // Pass  the value of $post to WordPress the insert function
                                // http://codex.wordpress.org/Function_Reference/wp_insert_post
    } // end IF
}

// Do the wp_insert_post action to insert it
do_action('wp_insert_post', 'do_insert');
?>


<!-- Put this in your theme template file -->
<div id="postbox">

    <form id="new_post" name="new_post" method="post" action="<?php bloginfo('template_directory');?>/post-process.php">

        <p><label for="title">Title</label><br />
        <input type="text" id="title" value="" tabindex="1" size="20" name="title" /></p>

        <p><label for="description">Description</label><br />
        <textarea id="description" tabindex="3" name="description" cols="50" rows="6"></textarea>
        </p>

        <p><?php wp_dropdown_categories( 'show_option_none=Category&tab_index=4&taxonomy=category' ); ?></p>

        <p><label for="post_tags">Tags</label>
        <input type="text" value="" tabindex="5" size="16" name="post_tags" id="post_tags" /></p>

        <p><input type="submit" value="Publish" tabindex="6" id="submit" name="submit" /></p>

        <input type="hidden" name="post_type" id="post_type" value="book" />
        <input type="hidden" name="action" value="post" />
        <?php wp_nonce_field( 'new-post' ); ?>

    </form>

</div>