Instead of using the 'single_template'
filter use the more generic 'template_include'
filter for both archive annd single post view:
add_filter('template_include', 'my_custom_templates');
function my_custom_templates( $template ) {
if ( is_single() && ( 'book_reviews' == get_post_type() ) ) {
if ( ! locate_template('single-book_reviews.php', false) )
$template = plugin_dir_path( __FILE__ ) . '/single-book_reviews.php';
} elseif( is_post_type_archive('book_reviews') ) {
if ( ! locate_template('archive-book_reviews.php', false) )
$template = plugin_dir_path( __FILE__ ) . '/archive-book_reviews.php';
}
return $template;
}
After that you have just to create the file 'archive-book_reviews.php'
in your plugin folder.