Amazon $10 off Kindle textbooks (books <$10 are free)e)

[maybekfire]

Some books are actually free if they are under $10.

Promo details/coupon code

Amazon.com: Textbooks

If you don't see the below, the book doesn't qualify:

"Kindle e-Textbook Promotion: This book qualifies for Kindle e-textbook promotions. If you’ve applied a valid promotion code to your account, the dollar amount of your code will be automatically applied when you buy this book with 1-click (promotions also apply on 1-click rental orders when a rental option is available)."

Examples of free books that qualify.
The Writer's Harbrace Handbook, 5th Edition $6.00
Jean Paul Sartre Basic Writings $4.49
Learn to Earn - A Beginner's Guide to the Basics of Investing and Business $8.35
The Ivy Portfolio: How to Invest Like the Top Endowments and Avoid Bear Markets $8.99
Introduction to Clinical Psychology: An Evidence-Based Approach, 1st Edition $5.54
Photoshop CS4: The Missing Manual: The Missing Manual $5.98
Selected Philosophical and Scientific Writings (The Other Voice in Early Modern Europe) $5.42
The Writer's Harbrace Handbook, 5th Edition $5.40
The Complete Art of War - Sun Tzu $9.89