diff --git a/src/build.sh b/src/build.sh
index ad2dd22..675dcf8 100755
--- a/src/build.sh
+++ b/src/build.sh
@@ -9,3 +9,5 @@ echo $FILES
 
 pandoc -o ../out/Spellblade.epub --resource-path=. title.txt $FILES
 ebook-convert ../out/Spellblade.epub ../out/Spellblade.mobi
+
+pandoc --lua-filter wordcount.lua $FILES
diff --git a/src/wordcount.lua b/src/wordcount.lua
new file mode 100644
index 0000000..517e4ac
--- /dev/null
+++ b/src/wordcount.lua
@@ -0,0 +1,30 @@
+-- counts words in a document
+-- from https://pandoc.org/lua-filters.html#examples
+
+words = 0
+
+wordcount = {
+  Str = function(el)
+    -- we don't count a word if it's entirely punctuation:
+    if el.text:match("%P") then
+      words = words + 1
+    end
+  end,
+
+  Code = function(el)
+    _,n = el.text:gsub("%S+","")
+    words = words + n
+  end,
+
+  CodeBlock = function(el)
+    _,n = el.text:gsub("%S+","")
+    words = words + n
+  end
+}
+
+function Pandoc(el)
+  -- skip metadata, just count body:
+  pandoc.walk_block(pandoc.Div(el.blocks), wordcount)
+  print(words .. " words in body")
+  os.exit(0)
+end