Add better code browsing instructions

README.md

@@ -19,9 +19,14 @@ for code examples for other editions, please see the following branches:
 
 ## Quick start
 
-All the code is in the [code](/code) folder. It is organized by language (terraform, bash, ruby, etc) and within each
-language, by chapter. Since this code comes from a book about Terraform, the vast majority of the code consists of
-Terraform examples in the [code/terraform folder](/code/terraform).
+All the code is in the [code](/code) folder. The code examples are organized first by the tool or language and then
+by chapter. For example, if you're looking at an example of Terraform code in Chapter 2, you'll find it in the 
+[code/terraform/02-intro-to-terraform-syntax](code/terraform/02-intro-to-terraform-syntax) folder; if you're looking at 
+an OPA (Rego) example in Chapter 9, you'll find it in the 
+[code/terraform/09-testing-terraform-code](code/terraform/09-testing-terraform-code) folder.
+
+Since this code comes from a book about Terraform, the vast majority of the code consists of Terraform examples in the 
+[code/terraform folder](/code/terraform).
 
 For instructions on running the code, please consult the README in each folder, and, of course, the
 *[Terraform: Up and Running](http://www.terraformupandrunning.com)* book.