Not yet, but it has been on my 'to read' list for a while now. In fact, it's been moving up in priority lately due to the main theme of the book, ideas I've encountered lately, and their reflection of my own life.
For example, a quote by Thomas Henry Huxley:
"The foundation of morality is to...give up pretending to believe that for which there is no evidence, and repeating unintelligible propositions about things beyond the possibilities of knowledge."
I've only really considered myself an unbeliever for about 4 years, but in defining myself that way (at least in how I live), I feel that I have actually acheived a more positive morality.
Long story short, I think that is the crux of this book and I am very interested in reading it