diff --git a/prep/README.md b/prep/README.md
index f7912a95c..3943f3088 100644
--- a/prep/README.md
+++ b/prep/README.md
@@ -10,6 +10,7 @@ Before you start this course, there's a few things we assume you've done:
 
 - You're familiar with the essentials of writing code in JavaScript
 - You have experience with JavaScript in the browser and in [Node](https://nodejs.org/en/)
+- You have read some of [How Computers Really Work by Matthew Justice](https://www.howcomputersreallywork.com/). You _must_ read chapters 1, 2, 7, 9, 10, 11, 12. Any other chapters may be interesting (feel free to read them! We particularly recommend 8), but aren't necessary.
 - You've completed the [Tour of Go](https://go.dev/tour/welcome/1)
 - Learnt about pointers and memory:
   - Read the [Pointers chapter](https://www.golang-book.com/books/intro/8) of [An Introduction to Programming in Go](https://www.golang-book.com/books/intro), and do the problems listed in the chapter.