I've read a lot of books on organizing. If I'm feeling stressed, and I feel like my "stuff" is taking over my life, I'll read another organizing book and then use this new knowledge to clean/declutter yet again.
This book was highly recommended by a blogger I follow. I'm glad I got it from the library and didn't pay for it. It wasn't a bad book, but if you've read any books on this topic before, you aren't going to learn anything new from this one. However, you will learn things like don't roll your socks into balls because it stresses them out. Not the material - but the sock itself. Unhappy socks make unhappy feet. Shirts piled on top of each other? You're suffocating them!
I'm reading another book that I bought on the subject: Banish Clutter Forever: How the Toothbrush Principle Will Change Your Life. I only paid $2 for it, but now it's selling for $10.
Not sure it will change my life, but after one chapter, I was motivated enough to get one room completely cleaned and another room started.