diff --git a/book/Makefile b/book/Makefile
index af41109..16e7343 100644
--- a/book/Makefile
+++ b/book/Makefile
@@ -32,6 +32,10 @@ help:
 html-linkcheck: clean html
 	@$(LYCHEE) "$(BUILDDIR)/html/"*.html
 
+# use watchexec to rebuild the HTML whenever a markdown file changes
+html-watch:
+	@$(WATCHEXEC) --shell bash -e css,md 'make clean html'
+
 # spell check all sources
 # NOTE: diagrams are not yet spell checked, but we emit the required changes
 codespell: