diff --git a/free-programming-books.md b/free-programming-books.md
index 1c6bbb901e8bbb98e29eee1f938b515df4b2f718..abef4cf111284e11f49893988b2bc4c2cb72783e 100644
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@@ -251,6 +251,7 @@
 * [The Art of Unix Programming](http://catb.org/esr/writings/taoup/html/) - Eric S. Raymond
 * [The Little Book of Semaphores](http://greenteapress.com/semaphores/) - Allen B. Downey
 * [Operating Systems and Middleware](https://gustavus.edu/mcs/max/os-book/) (PDF and LaTeX)
+* [Operating Systems: Three Easy Pieces](http://pages.cs.wisc.edu/~remzi/OSTEP/) (PDF)
 * [Practical File System Design:The Be File System](http://www.nobius.org/~dbg/practical-file-system-design.pdf) (PDF) - Dominic Giampaolo