diff --git a/book b/book
new file mode 160000
index 0000000000000000000000000000000000000000..22ed2a01aee872f055b5f5f212428f481cefc10d
--- /dev/null
+++ b/book
@@ -0,0 +1 @@
+Subproject commit 22ed2a01aee872f055b5f5f212428f481cefc10d