add_shortcode('author-name', 'author_name_shortcode_handler');

function author_name_shortcode_handler($atts,$content=null){
    if (!is_single()) return;

    global $wp_query;
    $user_id = $wp_query->post->post_author;

 	$name = get_user_meta($user_id, 'first_name', true) . ' ' . get_user_meta($user_id, 'last_name', true);

    if (!empty($name))
		return $name;
	else
		return;
}