add note for book

kengz · kengz · commit 7e8deff39355 · 2021-05-16T20:48:42.000-07:00
diff --git a/README.md b/README.md
@@ -9,6 +9,7 @@
   <br><br>
 </p>
 
+>NOTE: the `book` branch has been updated for issue fixes. For the original code in the book _Foundations of Deep Reinforcement Learning_, check out to git tag `v4.1.1`
 
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