diff --git a/themes/README.md b/themes/README.md
index 859330d..390408d 100644
--- a/themes/README.md
+++ b/themes/README.md
@@ -1,3 +1,3 @@
 # Themes
 
-Asciidoc themes use the YAML format.
+Asciidoctor has [great guides](https://docs.asciidoctor.org/pdf-converter/latest/theme/) on how you can go about theming your book.