I have the book and have done the exercises about five or six times and found them to be very releasing. I've only experienced the tremors/shaking a couple of times and found them to be minor, but worthwhile. What I've found is that you really have to maintain the positions for the amount of time that he indicates and in the manner he shows, and I use a stop watch to make sure I do. Even at that I will sometimes hold them longer just to get to the shaking mode. The sitting down against the wall for 5 full minutes is by far the most difficult and the one which really gets the legs to shaking - if you're doing it right.
I've done a lot of work and releasing and getting through my PTSD years ago with meditation but was looking to supplement my meditation with something else and found that this works fine. I sleep more soundly and have more energy during the day because of it and will keep it up.
If you read the book you will find that everybody faces trauma on a daily basis. Your birth was traumatic, your teen years and education were traumatic - life is traumatic. The American Way is to deny the trauma that we have in our lives and the more we deny our trauma or anything else, the more difficult it is to deal with it.
The book is available at most libraries and at Amazon it has twenty one five star ratings out of twenty one reviews - a set of ratings that I've never seen before. Along with those ratings are stories of rather amazing release too. What I like about the book is that he goes into the scientific explanation of how unprocessed trauma adversely affects the neurological pathways of the brain and produces toxins in our bodies. A lot of detailed information that the DVD may not have.
Here's the Amazon link with reviews: