diff --git a/book b/book
index 58aff04..af7b6bc 160000
--- a/book
+++ b/book
@@ -1 +1 @@
-Subproject commit 58aff048b10e95237f3b11917d1d3a5b85d8e0bb
+Subproject commit af7b6bc187ae7c6d5b8c174b44c9dff1b48ca269