diff --git a/README.md b/README.md
index 674cf40..384ba37 100644
--- a/README.md
+++ b/README.md
@@ -9,3 +9,11 @@ $ ruby -I. binary_tree_demo.rb
 $ ruby -I. XXX_demo.rb  # Etc...
 ```
 
+# What??
+
+Following along with this book [https://pragprog.com/book/jbmaze/mazes-for-programmers](https://pragprog.com/book/jbmaze/mazes-for-programmers)
+
+## Mazes included
+
+- BinaryTree binary_tree.rb  Chapter 2
+- Sidewinder sidewinder.rb  Chapter 2
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