First to say this book is not a quick fix, it takes a real investment of time, however in my experience it is well worth it. We are half way through the program and so far my son's writing has become more consistent in size, space wise, pressure and cursiveness. We have been working on his writing for many years and this has helped us to turn a corner. You do need to buy a fair bit of stuff, some of which you only use once, double sided blackboard, chalk, lots of big paper, different lead pencils, a light up pen, marker pens, paint, paintbrushes, gel pens, roller ball pens, a bandage.
The book works on developing muscle memory and helps children to feel their writing flowing. Time wise you need at least 1 big session (1 hour) a week plus 10 minutes daily to practice.