simply copy the files contained in the images folder of the book

README.asc

@@ -36,7 +36,7 @@ Do the following only once:
 
 ----
 $ mkdir images/
-$ find book/*/images/ -type f -and -name '*.png' -exec cp '{}' images/ \;
+$ find book/*/images/ -exec cp '{}' images/ \;
 ----
 
 Then you can build the book.