If you are a dedicated zhan zhuang practitioner and you would like to learn what it takes to reach the higher levels of skill in the practice, then yes this book is worth it. If you are just a dabbler I would say it is not really worth the money.
I practiced the 3 basic postures 20 min each for a couple of months and it is very effective when done that way. I stopped because I am now concentrating on spring forest qigong, which I find more effective for healing yourself and others.
I am willing to give my copy to someone and delete mine from my hard drive if anyone is really interested.