diff --git a/modules/book/book.install b/modules/book/book.install
index e92aca6..bd9d6de 100644
--- a/modules/book/book.install
+++ b/modules/book/book.install
@@ -14,6 +14,32 @@ function book_install() {
 }
 
 /**
+ * Implements hook_enable().
+ */
+function book_enable() {
+  // Enable node type, which may have been disabled if the module was disabled.
+  db_merge('node_type')
+    ->key(array(
+      'type' => 'book',
+    ))
+    ->fields(array('disabled' => 0))
+    ->execute();
+}
+
+/**
+ * Implements hook_disable().
+ */
+function book_disable() {
+  // Disable node type.
+  db_merge('node_type')
+    ->key(array(
+      'type' => 'book',
+    ))
+    ->fields(array('disabled' => 1))
+    ->execute();
+}
+
+/**
  * Implements hook_uninstall().
  */
 function book_uninstall() {