Part of the adventure that is restoring an early 911 is coming to terms with the often inaccurate and conflicting information available. The fact that during the mid-60s the Porsche Factory was geared less toward delivering an absolutely predicatble and consistent product doesn't help either.
The fact is, when attempting to restore an early car to original you're going to have to believe somebody, and basically this book is the Gospel.
True, the next edition really deserves colour photography (for that try "Original 911") -- but this book is really the most accurate assemblage of early 911 data I've found.
If you buy this book you have no excuse but to do a great job of returning your Porsche to it's beautiful, pristine and authentic state.
So buy it.