It's a "work in progress" in the sense that the professors aren't quite completely satisfied with it. It's still very readable, which is even more impressive when you consider the complexity of the topics being covered.

If you're interested, I'd recommend at least glancing at the 15-210 schedule[1] so you can see the order that the chapters are covered in the class.

[1]: http://www.cs.cmu.edu/afs/cs/academic/class/15210-s16/www/sc...