#10130: Prepare for building epub-format docs.
diff --git a/Doc/README.txt b/Doc/README.txt
index 03b1c7f..e386e87 100644
--- a/Doc/README.txt
+++ b/Doc/README.txt
@@ -54,6 +54,9 @@
 
  * "text", which builds a plain text file for each source file.
 
+ * "epub", which builds an EPUB document, suitable to be viewed on e-book
+   readers.
+
  * "linkcheck", which checks all external references to see whether they are
    broken, redirected or malformed, and outputs this information to stdout as
    well as a plain-text (.txt) file.