diff --git a/README.md b/README.md
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--- a/README.md
+++ b/README.md
@@ -1,3 +1,11 @@
 # book_runner
 
 run a command and put the output in a book
+
+## usage
+
+hold a single empty book (`default:book`) in your hand, and run:
+* `/run_in_book commandname args`
+
+the book will become a written book; the title will be the command name and arguments, the body will
+be the command output.