diff --git a/modules/README.md b/modules/README.md
index 5caf8d9..5271368 100644
--- a/modules/README.md
+++ b/modules/README.md
@@ -1,5 +1,11 @@
 # Nova Modules
 
+**TL;DR** — Nova's module library: two tiers of engine-agnostic modules,
+whose contract is declared in `interface.json` and translated by an adapter
+(Terraform today) to concrete infrastructure. This file explains how
+modules compose and how to add one; the L1/L2 tables and adapter detail
+follow below.
+
 Nova ships a two-tier module library. Modules are **engine-agnostic**:
 their contract is declared in `interface.json` (stack types like
 `aws:s3:bucket`), and an adapter translates the contract to a concrete