I should also note that I'm not generally a spiritual person; I don't regularily practice anything in particular. At the same time I am interested in and familiar with full-body spiritual practices and the Hindu and Buddhist faiths.
The book highlights the Universal Tao practice of sexuality, rather than Tantric-like practices, and does a good job of briefly explaining it's importance and foundations. At the same time, I sometimes found myself wondering more about the practice in general and how sexuality fits into the overall picture.
The chapters you'd think the book would touch on most of all: being a multi-orgamic couple, were similarily written: thorough and informative, but lacking in details and guidance. I do have some experience with spirituality practices, and have developed a fair bit of body and energy awareness through other activies. I found that I was barely able to experience what and follow some of the directions the authors were suggesting.
The book is also widely targeted to both naive and experienced users. However, in this broad targeting, I feel the authors managed to reach none of the groups fully. The instruction and guidance I bought the book for (sacred sex practices, something probably generally practiced by highly sexually aware couples) could be sparse. The information was there and complete, but it seemed to skip a whole level of pre-information one would have to know. Then the authors would explain very simple things you'd expect highly sexual couples to know, like the function and location of the clitoris, for instance: this is information anyone looking into this level of sexual encounter should probably know already.
Finally, the main thrust of the book is connecting with your partner, not being multi-orgasmic. After chapter 3, the book focuses on sharing energy, developing love, and a number of other very positive and beneficial practices that I'm glad I read about. Certainly, the authors do readers a service in not just giving them techniques without explaining their power and application. At the same time, this broad-based overview leaves the entire book lacking.
On the whole, this is a good book. It'll open your eyes to some new sexuality concepts, and I'm sure that as I continue to practice these concepts I'll develop a fuller, more spiritual sexuality. At the same time, I wouldn't recommend this book to anyone with no experience in spiritual or body-based practices like yoga, pilates, tai chi, martial arts, etc.: I would think one would have to develop some body awareness and control before being able to undertake some of the exercises.
More detail, more step-by-step, and exercises to get readers to that point would've made this an excellent resource. More information on multiple orgasm and how exactly to get to the point where you can feel and channel energy are, to my mind, critical. As it is, the authors are off to a good start but suplementation is necessary.
One final point: the book does include a section on intercourse and thrusting. Although this is soemthing a lot of couples can probably innovate in on their own, it is noteworthy in that this is one of the few sexuality resources I've ever seen that touches on the actual act of intercourse and the variety of possibilities there.