diff --git a/inc/admin/namespace.php b/inc/admin/namespace.php
index 1b7ddf6..0ea4914 100644
--- a/inc/admin/namespace.php
+++ b/inc/admin/namespace.php
@@ -7,6 +7,8 @@ namespace Aldine\Admin;
 
 use PressbooksMix\Assets;
 
+const BLOG_OPTION = 'pressbooks_aldine_in_catalog';
+
 /**
  * @param string $hook
  */
@@ -41,9 +43,9 @@ function update_catalog() {
 	$in_catalog = $_POST['in_catalog'];
 
 	if ( $in_catalog == 'true' ) {
-		update_blog_option( $blog_id, 'in_catalog', 1 );
+		update_blog_option( $blog_id, \Aldine\Admin\BLOG_OPTION, 1 );
 	} else {
-		delete_blog_option( $blog_id, 'in_catalog' );
+		delete_blog_option( $blog_id, \Aldine\Admin\BLOG_OPTION );
 	}
 }
 
@@ -64,7 +66,7 @@ function catalog_columns( $columns ) {
 function catalog_column( $column, $blog_id ) {
 
 	if ( 'in_catalog' == $column && ! is_main_site( $blog_id ) ) { ?>
-		<input class="in-catalog" type="checkbox" name="in_catalog" value="1" <?php checked( get_blog_option( $blog_id, 'in_catalog' ), 1 ); ?> <?php
+		<input class="in-catalog" type="checkbox" name="in_catalog" value="1" <?php checked( get_blog_option( $blog_id, \Aldine\Admin\BLOG_OPTION ), 1 ); ?> <?php
 		if ( ! get_blog_option( $blog_id, 'blog_public' ) ) { ?>disabled="disabled" title="<?php _e( 'This book is private, so you can&rsquo;t display it in your catalog.', 'pressbooks-aldine' ); ?>"<?php } ?> />
 	<?php }
 
diff --git a/inc/helpers/namespace.php b/inc/helpers/namespace.php
index 53f45ab..3c1c00c 100644
--- a/inc/helpers/namespace.php
+++ b/inc/helpers/namespace.php
@@ -7,47 +7,49 @@
 
 namespace Aldine\Helpers;
 
-use Pressbooks\Licensing;
-
 /**
- * Get catalog data.
- *
  * @param int $page
  * @param int $per_page
  * @param string $orderby
  * @param string $license
  * @param string $subject
+ *
+ * @return array
  */
 function get_catalog_data( $page = 1, $per_page = 10, $orderby = 'title', $license = '', $subject = '' ) {
-	if ( defined( 'PB_PLUGIN_VERSION' ) ) {
-			$request = new \WP_REST_Request( 'GET', '/pressbooks/v2/books' );
-			$request->set_query_params([
-				'page' => $page,
-				'per_page' => $per_page,
-			]);
-			$response = rest_do_request( $request );
-			$pages = $response->headers['X-WP-TotalPages'];
-			$data = rest_get_server()->response_to_data( $response, true );
-			$books = [];
-		foreach ( $data as $key => $book ) {
-			$book['title'] = $book['metadata']['name'];
-			$book['date-published'] = ( isset( $book['metadata']['datePublished'] ) ) ?
-				$book['metadata']['datePublished'] :
-				'';
-			$book['subject'] = ( isset( $book['metadata']['about'][0] ) )
-				? $book['metadata']['about'][0]['identifier']
-				: '';
-			$books[] = $book;
-		}
-		if ( $orderby === 'latest' ) {
-			$books = wp_list_sort( $books, $orderby, 'desc' );
-		} else {
-			$books = wp_list_sort( $books, $orderby );
+
+	if ( ! defined( 'PB_PLUGIN_VERSION' ) ) {
+		return [ 'pages' => 0, 'books' => [] ]; // Bail
+	}
+
+	$request = new \WP_REST_Request( 'GET', '/pressbooks/v2/books' );
+	$request->set_query_params(
+		[
+			'page' => $page,
+			'per_page' => $per_page,
+		]
+	);
+	$response = rest_do_request( $request );
+	$pages = $response->headers['X-WP-TotalPages'];
+	$data = rest_get_server()->response_to_data( $response, true );
+	$books = [];
+	foreach ( $data as $key => $book ) {
+		if ( ! get_blog_option( $book['id'], \Aldine\Admin\BLOG_OPTION ) ) {
+			continue; // Skip
 		}
-		return [ 'pages' => $pages, 'books' => $books ];
+		$book['title'] = $book['metadata']['name'];
+		$book['date-published'] = $book['metadata']['datePublished'] ?? '';
+		$book['subject'] = $book['metadata']['about'][0]['identifier'] ?? '';
+		$books[] = $book;
+	}
+
+	if ( $orderby === 'latest' ) {
+		$books = wp_list_sort( $books, $orderby, 'desc' );
 	} else {
-		return [ 'pages' => 0, 'books' => [] ];
+		$books = wp_list_sort( $books, $orderby );
 	}
+
+	return [ 'pages' => $pages, 'books' => $books ];
 }
 
 /**