diff --git a/book.toml b/book.toml
index 7fc6c560..4fbc347b 100644
--- a/book.toml
+++ b/book.toml
@@ -10,6 +10,7 @@ command = "./build.bash"
 
 [output.html]
 additional-js = ["js/moment.min.js", "js/index.js"]
+additional-css = ["css/style.css"]
 no-section-label = true
 git-repository-url = "https://github.com/rust-lang/rust-forge"
 edit-url-template = "https://github.com/rust-lang/rust-forge/edit/master/{path}"
diff --git a/css/style.css b/css/style.css
new file mode 100644
index 00000000..3f6f556d
--- /dev/null
+++ b/css/style.css
@@ -0,0 +1,3 @@
+:root {
+    --content-max-width: 1000px;
+}