I read the book last year, and really loved the concept.
I've never really done their specific diet, but I have tried to make changes one step at a time since reading the book- I typically am an "all or nothing" kind of gal, and quickly get burned out because I try to do too much at one time.
I set specific goals for myself, and did them one at a time. For instance, in preparation for my new diet, I did a few things like week one, no more caffeine (Yikes! that was the WORST one) then week two, no food at all with sugar- artificial or real- no candy, chocolate, ice cream, etc., Week three no processed snack foods- potato chips, pretzels, etc. Week four, exercise every single day.
That was basically my plan, and I've been able to stick by it almost 100% since I started, and I really think it's because I made all of my goals in stages, and did one thing at a time.
The book was so inspirational- I highly recommend it to anyone!